Detect charging or on wrist

Maybe I have something that suits your needs:
I wrote a little helper function to get only the isWearing value from HRM-raw.

Here a little example:

    checkIsWearing(
      (isWearingStatus, messages) => { print(messages[isWearingStatus ? 1 : 0]); },
      [
        "You are not wearing the watch.",
        "Yor watch is on your wrist or on a surface that appears similar."
      ]
    );

The return function is called with the isWearing-status as first and the passed data as second argument: returnFn(isWearing, data);

Here the code of this function:

    // define function to check if the bangle is worn by using the hrm
    function checkIsWearing(returnFn, data) {
      // create a temporary object to store data and functions
      global.tmpWearingCheck = {
        // define temporary hrm listener function to read the wearing status
        hrmListener: hrm => tmpWearingCheck.isWearing = hrm.isWearing,
        // set default wearing status
        isWearing: false,
      };
 
      // enable HRM
      Bangle.setHRMPower(true, "wearingCheck");
      // wait until HRM is initialised
      setTimeout((returnFn, data) => {
        // add HRM listener
        Bangle.on('HRM-raw', tmpWearingCheck.hrmListener);
        // wait for two cycles (HRM working on 60Hz)
        setTimeout((returnFn, data) => {
          // remove listener and disable HRM
          Bangle.removeListener('HRM-raw', tmpWearingCheck.hrmListener);
          Bangle.setHRMPower(false, "wearingCheck");
          // cache wearing status
          var isWearing = tmpWearingCheck.isWearing;
          // clear temporary object
          delete global.tmpWearingCheck;
          // call return function with status
          returnFn(isWearing, data);
        }, 34, returnFn, data);
      }, 2500, returnFn, data);
    }

I am using this in the 0.10+ version of sleeplog:
https://github.com/storm64/BangleApps/bl­ob/sleeplog_beta/apps/sleeplog/boot.js