Currently apps/widgets can do Bangle.setXYZPower, but you have an issue if one requests power and one tells the device to shut off.

An easy solution would be Bangle.setXYZPower(isOn, "myappname") - then we just store a list of 'myappname's that require something on and as long as there's something in there we keep it on. It's also backwards compatible.

Alongside this, Bangle.getXYZPower() should be added too.