This odd device is called the "Off". It is a coat hook which cuts the power when you hang anything from it, thus, supposedly, teaching you the value of electricity. This fully functional light switch is part of an experimental line of pluggable sculptures by Scott Amron, some useful, some rather terrible puns (the Firewall is a fire extinguisher with power prongs).
With a little rewiring, the "Off" could be a useful little gimmick; put one by the front door and you'll never leave the house lights on again. $35.
Product page [Dielectric]
