These three come up the most, and each takes a different approach to your data. Here are the Oura Ring 4, Garmin fēnix 8 and Apple Watch side by side (interactive compare).
| Oura Ring 4 | Garmin fēnix 8 | Apple Watch | |
|---|---|---|---|
| Score | 48 | 78 | 35 |
| API for you | Yes: Oura API v2 (OAuth app you register) | No: Connect APIs are partner-only | No cloud API: HealthKit on the iPhone |
| Bulk export | Membership Hub download | USB FIT files + full account ZIP | Health app export.zip (XML) |
| Works without vendor cloud | No | Yes, via Gadgetbridge | Partly: data stays on the phone, but you need an iPhone |
| Home Assistant | Community (cloud polling) | Community (cloud login) or Gadgetbridge | Paid third-party app (Health Auto Export) |
| Subscription | Required for the full app and the API ($5.99/mo or $69.99/yr) | Optional Connect+ ($6.99/mo or $69.99/yr) | None for data |
Oura: the best API, rented
Oura has the cleanest developer API of the three. The v2 REST endpoints return JSON for sleep, readiness, heart rate, workouts and more (docs). Since personal access tokens were deprecated in December 2025, even a personal script needs its own OAuth application (authentication). The bigger catch is that the API only works with an active Oura Membership. Oura’s own FAQ says non-members can’t use the API, but they can still download their data through the Membership Hub. Oura on the Web was retired on Oct 5, 2026 (Oura FAQ).
Tip: if you cancel, download your data from the Membership Hub first, then cancel.
Garmin: no developer API, but the files are yours
Garmin won’t give individuals API keys: the Connect Developer Program is for approved businesses. It doesn’t matter much, because the watch keeps its activities as FIT files, an open format with a public SDK, which you can copy straight over USB. You can also request a full account export from Garmin Connect. And Gadgetbridge supports modern Garmins, so you can skip Garmin’s cloud entirely. The paid Connect+ tier is optional, and Garmin says existing features and data stay free (announcement).
Apple Watch: very private, but locked to the iPhone
Apple doesn’t hold your health data in a cloud API at all. It lives in HealthKit on your iPhone (HealthKit), and Apple says Health data in iCloud is end-to-end encrypted (iCloud security overview). That’s great for privacy, but harder to get out and use: the only first-party export is a manual export.zip from the Health app (Apple guide). Automations require a third-party iOS app such as Health Auto Export, and it only runs while the phone is unlocked.
Which should you pick?
- You want to own the raw files and avoid the cloud: Garmin, paired with Gadgetbridge.
- You want a polished API to build dashboards on and don’t mind paying: Oura, but budget the membership as part of the cost of owning the ring.
- Your top concern is privacy from the vendor: Apple Watch, as long as you accept staying on iPhone and exporting by hand.
Scores and facts were last verified on 2026-10-20. Spotted something out of date? Suggest a correction.