Shake to toggle playback of metronome

I set my phone aside when I practice, and after I'm done, it's pretty likely that my phone would've turned itself off (I have power-saving mode on), so I'll have to unlock my phone ( I have a long password ) before finally being able to turn off the metronome. I think it'd be pretty nice if I could just shake my device to do that instead? Yeah I know 'shake' is already being used to set tempo but maybe this is a better use of the function? Or maybe add a start/stop metronome button to the widget if shake is unavaliable?