Makey Makey is a little circuit board that comes with a set of alligator clips. You can attach them to anything even mildly conductive (a body part, a glass of water, alphabet noodles, paper clips, Play-Doh, or fruit for example) and use that thing to control your computer as though you were hitting the keyboard or moving the mouse. The device plays well with the Arduino in case you want to attach it to simple sensors.