turn off sensors

On the latest firmwares, they keep track of which software request which hardware. For example something might say Bangle.setHRMPower(1,"widhrm"), and that info gets stored in Bangle._PWR.HRM, which is ["app"].

So, you could do Bangle._PWR.HRM = []; Bangle.setHRMPower(0) which would turn the HRM off. If you want to stop an app turning it back on at any point later, you could just change the function: Bangle.setHRMPower = function(){}