I read an article recently (I can't remember where, unfortunately) about an alarm clock that works with a wireless wristband accelerometer. You set a 1/2-hour window for the alarm to go off, and when it first senses movement during that window it sounds the alarm. The idea is that it's easier to wake up if you aren't in a deep sleep, and you don't move when you're in a deep sleep.
I think this is a great idea, but I don't want to shell out the money for the clock when my N800 should be capable of doing the same thing, as long as I can find a suitable accelerometer. Is anyone interested in this? Any ideas for a bluetooth accelerometer? I suppose you could strap a Wii-mote to your wrist, but that seems a bit big .