Is it possible to get heart rate updates from a Androidwatch in my app?

Question

I have an Android app and I want to read the heart rate from any connected Android watch (Wear OS, Tizen, etc). Is this possible without developing a wearable app?

I tried registering a listener on the Sensor.TYPE_HEART_RATE but I don't see any of the 3 watches that I have show up (Ticwatch E, Ticband, Gear S2). I ensured I request the Manifest.permission.BODY_SENSORS permission.

sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager?

    heartRateSensor = sensorManager?.getDefaultSensor(Sensor.TYPE_HEART_RATE)

    val registered = sensorManager?.registerListener(this, heartRateSensor, SensorManager.SENSOR_DELAY_NORMAL)
    Log.i(TAG, if (registered!!) "Registered Listener" else "Failed to register listener")

Answer 1

I did some research using an Android Wear watch, Samsung Gear S2, random heart rate fitness tracker watch (Ticwatch) and a standalone bluetooth heart rate arm band.

Just to reiterate my goal was to read heart rate data from the watch's sensor through my phone app without making a watch app.

My findings were as follows:

1. The code sample I posted above was in my phone app and the SensorManager only works with sensors that are built into the device. For example, if the app was running on the phone I would only get sensors on the phone, if on the watch I would get the ones on the watch. This obviously didn't work as no heart rate sensors showed up unless the phone had one built it. The same code in a watch app worked and I was able to get the heart rate that way.
2. Using the Fitness API and Samsung Health API I was able to get updates on the phone app when the heart rate was read. Only problem with this solution was you can't set the frequency of heart rate readings. To save battery life it looks like most watches cap the interval at every 10 minutes when still or every few seconds during a workout. This also didn't work as I needed more frequency updates.
3. The bluetooth heart rate armband was the only was I was able to get the heart rate read at the frequency I wanted. This solution required pairing to the monitor but it was a simple connection and I did not need to develop any watch apps!

I hope this clarifies how the SensorManager only works for sensors on the device the app is running on.