Trying to ignore the alarm isn't going to work with the Princess in a Pea Alarm Clock (PPAC). Jeff Saltzman rigged an air compressor to lift up one side of a mattress when it's time to wake up. If the sleeper doesn't get up, s/he'll get thrown to the floor.
Link via Make
UPDATE 12/14/09: I've swapped out the video. Thanks, GlitchEnzo!