MAKE Weekend Projects - Monkey Couch Guardian

I invented the Monkey Couch Guardian, and wrote a how-to so you can build one, too.

Combine an Arduino with a proximity sensor, and make an obnoxious device to discourage cats and other fur-shedding pets from jumping on beds and couches. This project will also introduce you to the SPDT relay, a fundamental component of hobbyist electronics projects.
Monkey Couch Guardian: complete instructions