The Paint On Firewall.

DefendAir from Force Field Wireless is a latex house paint that has been laced with copper and aluminmum fibers to form an electromagnetic shield that blocks most radio waves and protects wireless networks. Available (for now) in flat gray, one coat can shield WiFi, WiMax, and Bluetooth networks ranging from 100 MHz to 2.4 GHz.

This was so funny I had to post it!