Solarbotics Solarbotics Useless Box Kit
Yes, it's ... Useless! Designed as featured over at Makezine.com. It's a clever electromechanical box that turns itself off after you've turned it on. This is now a full kit, complete with Solarbotics satisfaction warranty, but you will have to assemble it (requires some soldering), supplying your own soldering gear, batteries, and screwdriver.
Solarbotics Useless Box Kit
Usually ships in 1-3 business days.