Syncing the Galaxy Watch on Android without Samsung Health

When I started building FitMesh, the apparently easiest path was using Samsung Health as the data source. I figured out the catch early: Samsung Health doesn't expose a stable, public API for third parties to read raw data on Android. It existed, then it was deprecated, then it came back in a different shape, and today it's effectively a walled garden.

The right path: Wear OS Health Services

Health Services is Google's official API for biometric data on Wear OS. It works like this:

1. You install a small client on the wearable (a Wear OS app)
2. The client registers as a listener for the data you want: HEART_RATE_BPM, STEPS_DAILY, CALORIES_DAILY, and so on
3. The data streams in while the user wears the watch
4. Periodically, the client syncs it to the phone via the Wearable Data Layer
5. On the Android phone, the FitMesh app receives it and forwards it to the backend

The traps I hit along the way

Battery drain. Initially I was sampling heart rate every 5 seconds. Result: a dead watch in 6 hours. I switched to MEASURE_TYPE_DAILY for aggregates and on-demand sampling only during an explicit workout.

Permissions. The user has to grant permissions on the phone and on the watch, separately. I had to design an experience that makes this two-step flow obvious without confusing anyone.

Offline-first. The watch isn't always connected to the phone. The Wear OS client writes to a local SQLite store, and the sync runs as soon as the Data Layer reconnects.

What I'd do differently

I would adopt androidx.health.connect.client as an additional layer: it lets you read data from other health apps too (Strava, Adidas, and so on), expanding the user base without writing custom integrations.

For now, the "Watch → Phone → Cloud" design works, but I have the feeling the right model is "Watch → Health Connect → Apps". We'll see if Google actually gets there.