Isn't it already does? I am running KoReader on rM1 for eReader purposes. It works this way: I start by long press of the middle button on rM1. To switch back, I quit KoReader and it restarts built in UI utility. It needs small service running in background. The only issue I've noticed is with battery life which seems the same even in a sleep mode. I am curious is that because of this small service that ignores sleep mode?