Unlike other alarm clocks, the "Princess and the Pea" uses an air compressor to inflate the mattress and literally throw you out of bed. Powering this thing is "a homemade Arduino-compatible board and a power block under the night stand for power and relays driving the sprinkler valve." Video after the break.
The "pea" is actually an inflatable bag that rests under the mattress. Where you'd normally hear an ear-piercing alarm, here you'll feel your bed rising up under you until your weight makes the bed seesaw, forcing you off.[via Dvice]