Wake’n'Shake is a simple and efficient iPhone app that test your sleepiness. The alarm turns off when you shake the phone for a while but if you stop stirring, it starts counting time from scratch.
This remind me of Seinfeld:
“Jerry: Did you shake it up?
Jerry: You gotta shake it up.
Elaine: No. I’m sick of shaking. You’ve got to shake everything.
Jerry picks up the bottle and shakes it gently.
Jerry: Yeah, that’s a real nuisance. This is killing me.”