littleBits has a bunch of awesome educational kits for kids. The Rule Your Room Kit is for touch-activated inventions. It has 8 inventions, allowing your kids to make a burglar buzzer, top secret safe, buzzing booklet, and domain defender.
The kit comes with buzzer, sound trigger, dimmer, servo, and other parts needed for fun projects. These bits are all reusable. Costs $99.95 at this time.