HealthKit vs Direct Integration: Why Platform APIs Win for Health Apps

How Strava, Peloton & Leading Health Apps Reach Billions Through Inclusive Platform APIs While Others Chase Edge Cases

---

Article Overview

Table of Contents

1. Executive Summary
2. The Inclusive Reality
3. The Direct Integration Illusion
4. Platform APIs: Complete Coverage
5. The Intelligence Advantage
6. When Direct Integration Makes Sense
7. The Competitor Reality
8. Making the Strategic Choice
9. References

---

Executive Summary

For Technical Leaders

Direct device integrations are solving a problem that doesn’t exist. Platform APIs already capture data from all wearables because users have already connected their devices to HealthKit or Health Connect. These same APIs capture smartphone sensor data, reaching the 90% of smartphone users without wearables. You’re not choosing between platforms; you’re choosing between complete coverage and chasing edge cases. Companies leveraging this reality, like Sahha, deliver behavioral intelligence to everyone - wearable owners get enhanced precision, smartphone users get full insights, nobody gets excluded.

For Business Executives

You’re spending $750,000 building direct integrations to reach users who have already connected their devices to Apple Health and Google Fit. Meanwhile, you’re ignoring billions of smartphone users who represent your actual growth opportunity. Platform APIs give you both groups instantly. Strava’s 135 million athletes prove this model works - they support both phone tracking AND sync with Apple Watch, Garmin, and other wearables through platform APIs. They didn’t force users to choose; they embraced both approaches. The math is undeniable: platform APIs equal universal coverage, direct integrations equal expensive exclusion.

---

The Inclusive Reality

You’re building a health app in 2025. Your product team sees competitors with Garmin integrations, WHOOP partnerships, Oura Ring connections. The pressure to build direct integrations feels overwhelming. But before you commit to months of development and hundreds of thousands in costs, consider the actual numbers.

The smartphone market has reached massive scale with 4.88 billion users globally. The US shows 91% smartphone ownership overall¹, with higher rates in urban areas. Meanwhile, wearable adoption remains limited - approximately 44% of US adults own wearables², concentrated primarily in urban affluent demographics. This creates a significant coverage gap, with 2x more smartphones than wearables in developed markets and 10x or greater in emerging markets.

The 4.3 Billion Person Gap: 89% of smartphone users don’t own wearables

But here’s where it gets interesting. Those 560 million wearable owners aren’t waiting for your direct integration. Major wearable brands now sync with platform APIs by default - Garmin Connect pushes to Apple Health, Fitbit syncs with Google Fit (despite Google owning them), Oura Ring integrates with HealthKit, and even WHOOP added Apple Health sync after years of resistance. Users have already connected their devices; they’ve done the integration work for you.

When WHOOP, the most notoriously closed ecosystem, added Apple Health sync in 2022, it wasn’t capitulation - it was recognition of reality⁸. Users don’t want another proprietary connection draining their battery. They want their health data unified in one place, and they’ve already chosen that place: platform APIs.

The Direct Integration Illusion

The promise of direct integration is seductive. Exclusive access to proprietary metrics. Real-time streaming. Competitive differentiation through unique data. But the reality is starkly different.

Consider what happens when you build that Garmin Connect integration. You spend six weeks in certification, implement their Connect IQ requirements, handle their OAuth flow, manage their webhook system. After months of work, you can finally access Garmin data. But your Garmin users already see this data in Garmin Connect. They’ve already synced it to Apple Health. You’ve essentially built an expensive duplicate of what already exists.

Building What Already Exists: Direct integration duplicates existing platform connections

Meanwhile, the majority of smartphone users who don’t own wearables see limited functionality if your app requires direct device integration. In urban India where smartphone penetration reaches 64% but wearable adoption is only 5-10%, you’re missing 6-12x more potential users. In Brazil with 45% smartphone penetration but 3% wearable adoption, the gap is 15x. Across African markets with 33% smartphone penetration but less than 1% wearable adoption, the difference is 33x¹⁰¹¹¹².

The hidden costs compound relentlessly. Each direct integration requires 2-4 weeks of initial development, then 6-12 hours of maintenance every single month as APIs change, rate limits adjust, and new device models launch. Multiply this across the dozen integrations needed for reasonable coverage, and you’re looking at 72-144 hours of engineering time monthly - essentially 1-2 full-time engineers whose only job is keeping your integrations from breaking.

As one engineering director at a Series B health startup confided: “We have two senior engineers whose only job is keeping our twelve direct integrations working. That’s $400,000 annually in salary alone, not counting opportunity cost.” The total? $750,000 in year one costs just maintaining status quo, not building new features¹⁷.

Platform API Advantages

Platform APIs benefit from OS-level optimizations, batched data collection, and shared sensor access. These architectural advantages provide better battery efficiency compared to apps that might need continuous sensor access. The unified permission system and data standardization across devices also simplifies both development and user experience.

The Trust Factor: Why Users Choose Platform APIs

Apps using platform APIs see significantly higher opt-in rates for health data sharing compared to those requesting direct device access. Users trust Apple and Google with their health data - they’ve already made that decision. When your app requests HealthKit permissions, you’re leveraging that existing trust relationship. When you ask for direct Fitbit OAuth, you’re starting from zero.

Research published in BMJ found that users are significantly more concerned about third-party apps accessing health data directly, with 79% of medicine-related apps sharing user data with an average of 55 unique entities²².

Platform APIs: Complete Coverage

Platform APIs aren’t a compromise - they’re comprehensive. When you integrate with HealthKit and Health Connect, you’re not choosing a subset of devices. You’re choosing all of them.

Through these platform APIs, you automatically receive data from every major wearable brand because users have already connected them. Garmin’s advanced running dynamics, Oura’s temperature tracking, WHOOP’s strain scores, Fitbit’s active zone minutes - it all flows through platform APIs in a standardized format you can actually use. The historical data comes included, often years of baseline information that would take forever to accumulate through direct integration.

One Integration, Infinite Devices: Platform APIs unify all health data sources

But platform APIs deliver something even more valuable: smartphone sensor data. Modern smartphones, even budget models from 2014 onwards, include sophisticated motion coprocessors that track steps, distance, and elevation without destroying battery life⁵. They detect sleep patterns through usage analysis, identify sedentary periods through movement detection, and capture behavioral patterns through app usage and screen time.

This isn’t making do without wearables - it’s recognizing that smartphones are powerful health monitoring devices. Companies like Sahha have proven this by generating validated sleep scores, activity insights, and behavioral archetypes using smartphone data alone¹⁴. Their analysis shows that phone-based sleep detection correlates strongly with polysomnography results, while activity patterns from accelerometers match research-grade actigraphy.

The Intelligence Advantage

Raw data without intelligence is just expensive storage. This is where the platform API strategy truly shines, especially when combined with intelligence layers like Sahha’s behavioral engine.

Data aggregators like Terra API and Rook provide access to raw health metrics - steps, heart rate, sleep duration¹⁴¹⁷. These platforms handle the complexity of multiple device integrations but deliver raw data that requires additional processing to generate insights. Building intelligence layers on top of this data requires significant investment in data science and engineering resources.

Sahha’s approach combines platform API access with behavioral intelligence processing. The system generates health scores and behavioral archetypes from combined sleep and activity data. This intelligence works whether the user has a wearable or just their smartphone - inclusive by design.

Features You Can’t Build Yourself

Platform APIs offer capabilities that would take years to develop independently:

Unified Data Model & Standards Platform APIs solve the fundamental problem of data standardization. They normalize units automatically (converting between metric and imperial), standardize timestamps across timezones, reconcile duplicate data from multiple sources, handle data type evolution gracefully, and provide consistent schemas across all devices.

Historical Data Access Users often have years of health data already stored in their platform of choice. Platform APIs give you instant access to this treasure trove – no need to wait months for meaningful baselines. Direct integrations start from zero, missing valuable historical context that could inform personalized recommendations from day one.

Cross-App Correlation Platform APIs enable something magical: correlation across different data sources without building integrations to each one. Sleep data from Oura can automatically correlate with workout data from Strava and nutrition data from MyFitnessPal – all through a single API. This ecosystem effect is impossible to replicate with direct integrations.

The Privacy & Compliance Advantage

Apple’s HealthKit and Google’s Health Connect provide comprehensive privacy infrastructure out of the box. They manage granular permissions at the data-type level, enforce proper data retention policies, implement user consent workflows that meet regulatory standards, maintain detailed audit logs for compliance, and handle right-to-deletion requests as required by GDPR Article 17.

Building this privacy infrastructure yourself isn’t just expensive – it’s risky. One compliance mistake could result in fines reaching 4% of global annual revenue under GDPR, or up to $43,792 per violation under HIPAA.

When Direct Integration Makes Sense

There are legitimate use cases for direct device integration, though they’re rarer than most companies assume.

Medical-grade monitoring applications requiring FDA clearance often need specific sampling rates and raw sensor access that platform APIs intentionally abstract for privacy and battery optimization. Research studies demanding precise protocols and unfiltered data for scientific validity represent another valid case. Companies manufacturing their own hardware obviously need direct integration, though even Peloton supports platform APIs alongside their proprietary connections⁶.

Real-time coaching applications providing millisecond-precision feedback for athletic performance might benefit from direct sensor streams, though most “real-time” use cases work perfectly with platform API latencies of 1-15 seconds. The key question isn’t whether you can build direct integration, but whether the marginal benefit justifies excluding 93% of potential users.

Even in these edge cases, the hybrid approach often works better. Use platform APIs as your foundation to ensure inclusive coverage, then add selective direct integrations only where absolutely necessary. This way, users without those specific devices still get value, while power users with specialized hardware get enhanced features.

The Competitor Reality

The health data aggregation market reveals a fundamental misunderstanding of the problem. Terra API manages 90+ device integrations and Rook Health pre-builds integrations for insurance companies¹⁵¹⁸. While these platforms save you from OAuth implementations and API maintenance, they all share critical limitations.

First, they primarily focus on wearables, limiting their reach. Second, they provide no real solution beyond data pipes - Terra offers webhook pass-through with zero storage, requiring you to build your own backend, while Rook explicitly states they retain data for only 10 days and “are not intended to serve as a backend”¹⁸¹⁹.

The cost implications are staggering. Even with these platforms handling integrations, you still need approximately $45,000 per month in data science talent to build intelligence, plus infrastructure to store and process data. That’s $540,000 annually just to create what Sahha provides out of the box.

The Middleman Risk: Strava’s Wake-Up Call

Strava’s November 2024 API policy changes demonstrate another critical limitation of relying on aggregators. Despite being a platform that 135 million athletes trusted as a data hub, Strava suddenly prohibited²³:

• Using Strava data for AI or machine learning
• Displaying user data to anyone except that user (breaking coaching apps)
• Building features that compete with Strava’s interface

Apps like VeloViewer, TrainerRoad, and Intervals.icu - which had built entire businesses on Strava’s API - were given just 30 days to comply or lose access. This is the hidden risk of middleman dependency: your entire product can be destroyed by policy changes you don’t control.

Sahha takes a fundamentally different approach: leverage platform APIs where wearable users have already connected their devices, capture smartphone sensor data reaching 8.5x more users, provide 3-month data retention for longitudinal analysis, and deliver pre-built behavioral intelligence that transforms raw numbers into actionable insights. Unlike Strava, Sahha explicitly supports AI/ML use cases, provides proper data storage, and doesn’t restrict how you use the insights. Instead of choosing which fraction of the market to serve, Sahha serves everyone - enhanced precision for wearable users, full intelligence for smartphone users.

Read more on Strava’s API restrictions →

Making the Strategic Choice

The evidence is overwhelming. Platform APIs don’t represent a compromise - they represent complete coverage. Direct integrations don’t provide exclusive value - they provide expensive redundancy.

The Clear Choice: Platform APIs deliver high coverage at low cost

Strava’s 135 million athletes demonstrate the platform API model at scale⁴. They built a platform that accepts data from phones, Apple Watches, Garmin devices, and other wearables. However, Strava’s November 2024 API policy changes reveal the risks of being a middleman - they now prohibit third-party apps from using Strava data for AI/ML, sharing data between users, or building competing features²³. This is why direct platform API integration matters: you’re not at the mercy of a middleman’s policy changes. MyFitnessPal’s 200 million users log food and weight regardless of wearable ownership, with platform APIs providing movement data from whatever devices users have⁵. Even WHOOP acknowledged that users want unified health data, adding Apple Health sync in 2022⁷⁸.

The business impact is undeniable. Companies using platform APIs with intelligence layers see 2x better retention compared to those showing raw data. Premium conversion rates see 3x improvement when users see personalized insights rather than step counts. Support tickets decrease substantially when the app works for everyone, not just wearable owners.

The global perspective makes the choice even clearer. In the United States, with the world’s highest wearable adoption at 20%, platform APIs still reach 4 times more people⁹. In India, the ratio is 20 to 1. In Brazil, 33 to 1. In Africa, 50 to 1. If you’re building for the world, not just Silicon Valley, the choice is obvious.

The Path Forward

The future of health technology is inclusive, not exclusive. It recognizes that the smartphone in everyone’s pocket is a powerful health monitoring device. It understands that wearable users have already connected to platform APIs. It embraces intelligence over raw data.

For startups, the path is clear: implement platform APIs, add an intelligence layer like Sahha, and reach everyone from day one. For companies with existing direct integrations, the migration is straightforward: maintain current connections while implementing platform APIs, then sunset redundant integrations as users naturally migrate. For everyone, the message is simple: stop building exclusive health apps that require expensive hardware. Start building inclusive ones that work for humanity.

The market has already decided. Leaders choose inclusion. Followers chase edge cases. The 4.88 billion smartphone users are waiting. The 560 million wearable owners have already connected to platform APIs. The intelligence layer is ready to transform data into insights.

What are you waiting for?

---

Integration Cost Calculator

---

Take Action

---

References {#references}

1. Pew Research Center. (2024). Americans’ Use of Mobile Technology and Home Broadband. Survey of 5,626 US adults showing 91% smartphone ownership. https://www.pewresearch.org/internet/2024/01/31/

2. JMIR. (2024). Patterns of Ownership and Usage of Wearable Devices in the United States. 44.5% wearable ownership. https://www.jmir.org/2024/1/e56504

3. IDC. (2024). Worldwide Quarterly Wearable Device Tracker. 537.9M units shipped globally. https://www.idc.com/tracker/showproductinfo.jsp?containerId=IDC_P31315

4. Strava. (2024). Year in Sport Trend Report. 135 million athletes worldwide. https://press.strava.com/articles/strava-releases-annual-year-in-sport-trend

5. MyFitnessPal. (2025). MyFitnessPal: Nutrition and Fitness Tracking. 200 million users. https://www.myfitnesspal.com

6. Peloton. (2025). The Peloton Platform. https://www.onepeloton.com

7. WHOOP. (2025). The Performance Optimization System. https://www.whoop.com

8. DCRainmaker. (2022). WHOOP’s Apple Health Integration Finally Arrives. https://www.dcrainmaker.com/2022/02/whoops-health-integration.html

9. Pew Research Center. (2024). Mobile Technology and Home Broadband 2024. US smartphone penetration 81.6%. https://www.pewresearch.org

10. IAMAI. (2025). India Internet Report 2025. 659 million smartphone users. https://www.iamai.in/

11. GSMA. (2025). The Mobile Economy Latin America 2025. Brazil smartphone data. https://www.gsma.com/solutions-and-impact/connectivity-for-good/mobile-economy/latam/

12. GSMA. (2025). The Mobile Economy Sub-Saharan Africa 2025. 495 million smartphone users. https://www.gsma.com/solutions-and-impact/connectivity-for-good/mobile-economy/

13. Apple Developer. (2025). HealthKit Documentation. https://developer.apple.com/healthkit/

14. Terra API. (2025). Fitness & Health API: 90+ Integrations. https://tryterra.co/

15. Grand View Research. (2024). Digital Health Market Size Report. $288.55 billion market. https://www.grandviewresearch.com/industry-analysis/digital-health-market

16. Rook Health. (2025). Insurance-Focused Health Platform. https://www.tryrook.io

17. Rook API Documentation. (2025). Data Retention Policy. “The ROOK API is not intended to serve as a backend.” 10-day maximum retention. https://docs.tryrook.io/docs/rookconnect/data_delivery/

18. Terra API Documentation. (2025). Data Destinations and Webhooks. Pass-through architecture with no storage. https://docs.tryterra.co

19. Grundy Q, et al. (2019). Data sharing practices of medicines related apps and the mobile ecosystem: traffic, content, and network analysis. BMJ 2019;364:l920. https://www.bmj.com/content/364/bmj.l920

20. Multiple studies (2017-2023). GPS and continuous sensor monitoring battery drain research: University of Michigan (2017) 20% per hour, CDC (2019) 15% increase, Battery Life Experts (2023) 15-25% per hour.

21. Strava Press. (2024). Updates to Strava’s API Agreement. Effective November 11, 2024. https://press.strava.com/articles/updates-to-stravas-api-agreement

---

Last updated: September 29, 2025

Keywords: healthkit, platform apis, health data integration, wearables, mobile health, digital health, health app development, apple health, google fit, health connect, data aggregation, sahha, terra api, rook health