On a PC, when turned off, the motherboard has a lithium battery to maintain the clock, and virtually all modern bioses have the ability to wake up on real-time-clock alarm. I use a pc running linux as a pvr, and it powers up/down regularly to make recordings. The pvr app (MythTV) writes the scheduled wake-up time into the bios and powers off. Do android phones not have some sort of bios mechanism? I've noticed mine keeps time when powered off; even if the time settings in the phone are set to manual (i.e. not using the cellular network for time management), so it must be doing it somehow. If there's no wake-up on rtc feature, then I guess it's not possible to automatically wake-up due to hardware limitation. Maybe a little food for thought for developers?