Detect charging or on wrist

Is it possible to detect whether a bangle.js2 is either on charge or (preferably) not on a wrist? If so I want to look in to possibly creating an app to silence the vibration/notification in those circumstances. I've tried a search using the obvious terms and cannot find anything that already exists.

For charging there is Bangle.isCharging.
"Not on a wrist" is tricky, but I guess you could use the accelerometer and check if there is no movement for a certain period. Maybe even check for x and y being zero if you always place it face up/down.

Checking heart rate could work?

Thanks. I like the "face down" tip. That looks like it may be what I'm looking for.

I installed the SleepLog app yesterday, that says it uses the internal temperature sensor to help identify if it's on a wrist, there might be something in that app you could reuse rather than start from scratch.

Ta. That could work for removal, but I was also hoping to pause heartrate monitoring when removed as well as silencing. Perhaps a hybrid approach might work, with movement/orientation switching is back to "being worn" mode. All good food for thought...

Great - I'll take a look. I also saw an app that scheduled silent times, so I was going to look at the code for that as well to see what I could "borrow".

You could use movement from http://www.espruino.com/Reference#l_Bangle_getHealthStatus to detect if the Bangle is moving around at all, and also the HRM-raw event that comes from the HRM on Bangle.js 2 has a field for whether it thinks the Bangle is being worn (eg if something is close to the HRM) - but if the Bangle is on a table then it could still be fooled.

Ta - I'll look into the HRM event as well. Lots of options to research!

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

If you want another example of the thermometer-solution, it's implemented in the app 'Activity Reminder'.