Resolved: advertising a GATT service (heart rate) does not work but UART does

Hi, maybe just try:

  Bangle.setHRMPower(1);
  NRF.setServices({
    '180d': {  // Heart Rate Service UUID
      '2a37': {  // Heart Rate Measurement Characteristic UUID
        value: [0x00, 0x00],  // Initial value: HRM not available
        broadcast: false,
        readable: true,
        notify: true,
        description: "Heart Rate Measurement"
      }
    }
  }, { advertise: ['180d'] });  
  Bangle.on('HRM', function(hrm) {
    try {
      NRF.updateServices({
        '180d': {
          '2a37': {
            value: [hrm.confidence, hrm.bpm],
            notify: true
          }
        }
      });
    } catch (e) {
      NRF.disconnect();
    }
  });

No need for the onInit stuff.

You'll need to connect to the Bangle after you run the app. The NRF.disconnect() in the try...catch will force the Bangle to disconnect if you'd forgotten to disconnect before (if the services hadn't updated) and then you'll have to reconnect