Fliptheplate.com sells the most advanced stealth license plates on the market.

The flipping licensed plate device allows two license plates. With just a flip of a switch, you can flip your plate down to a 180 degree angle “Out of Sight”. The most obvious application for this stealth license plate is to avoid cameras used on toll roads or at red lights. It's aslo designed as an easy way to keep your plates clean when you’re off-roading, or to protect your identity when showing off your whip at a car show.