HRM is requested it searches on Bluetooth for a heart rate monitor, connects, and sends data back using the `Bangle.on('HRM')` event as if it came from the on board monitor.
**To disable this and return to normal HRM, uninstall the app or change the settings**
### Modes
* Off - Internal HRM is used, no attempt on connecting to BT HRM.
* Default - Replaces internal HRM with BT HRM and falls back to internal HRM if no valid measurements received.
* Both - The BT HRM needs to be started explicitly by an app that wants to use it. BT HRM has its own event and is completely separated from the internal HRM. Apps not supporting the BT HRM will not see the BT HRM measurements.
* Custom - Combine low level settings as you see fit.
The recorder plugin can record the BT HRM event (blue) and the original unchanged HRM event (green). This is mainly useful for debugging purposes or comparing the BT with the internal HRM, as the resulting "merged" HRM can be recorded using the default HRM recorder.
