How does one tinker’s device unlock strangers’ cars and garages?

Tinker Samy Kamkar developed a $32 radio device smaller than a cellphone – which he calls RollJam – that can open most modern vehicles and garage doors. It works by simply getting between the owner’s real opener and his or her vehicle or garage door and intercepting the signal, memorizing it and using it later to open the door when the owner isn’t around.

Kamkar reported that the device works on Nissan, Cadillac, Ford, Toyota, Lotus, Volkswagen and Chrysler vehicles, Cobra and Viper alarm systems, and Genie and Liftmaster garage door openers.