I'm a student in electrical engineering, and I made this device for fun over the summer. You clap 5 times, and it figures out the angle to you, turns to you, and shoots a Starburst at you. It uses two microphones to sense the direction, kind of like a cheap passive sonar (the time difference in when the sound hits the microphones can tell you the angle). It's controlled by a microcontroller, which is a tiny, very cheap (like $6) computer on a chip. Click here for the details of how it works.