Out of Bed Alarm

Anyone who puts kids to bed knows they don't always stay in bed.  Today's good idea is an alarm for the kids bed that would sense when they were out of bed.  It would be weight based so if the kid gets off the bed an alarm goes off and the only way to shut it off is to get back on the bed.  That'll keep the little rascals out of the fridge.  You would also have a timer on it so when the kids get up in the morning the alarm is turned off when the head to the little persons room.