Currently I have the following devices: Huawei Watch and a polar H7 (which syncs with Google Fit through the Polar App).
I try to detect which devices logged to Google Fit but in the documentation I cannot find anything. Is there a way to add a tag to a reading or something?
Try to claim the polar device with the help of BLE API and you can start with startBLEscan, you will be getting the list of BLE devices which have to be paired initially and shouldn't be paired with other applications. Once you get the device go for claiming those devices, and then with the help of Sensor API you can get the data from those devices.
Hope I didn't made it confusing
Use the following link for more suppourt https://developers.google.com/android/reference/com/google/android/gms/fitness/BleApi