Speaking of aluminum foil, it also works to block the RFID chips in the new CA driver's licenses. I read a post where a man with some sort of legal problems was getting pulled over by the police at least once a month for no apparent reason. Then when his friend was giving him a ride, his friend got pulled over! This made it pretty obvious the police scan our new "enhanced" driver's licenses as we drive by. He then put aluminum foil over his RFID chipped driver's license and voila! The police are no longer pulling him over. Seems like those tin foil hat folks were on to something after all!