image taken from: http://www.sowbug.com/ok-wake

Mike Tsao published a nice work with AVR microcontrollers. He realized a smart wake-up timer for his kids who are too young to read the clock. Half an hour before the desired wake-up time, the smart wake-up timer begins to pulse with a low frequency with a red LED, increasing the frequency until the wake-up time is reached. Then the wake-up timer signals shows a green LED, which means that it is ok for the kids to wake-up the parents.

This electronic solution definitely solves a problem every parents have, thanks a lot Mike!