An attack I have read about involves cars that are equipped with "Smart Entry" where the key remains in your pocket/purse and when you touch the door handle or approach the car it sense the key and unlocks. The attacker gets a transceiver off the mysterious Internets! (its a series of TUBES!). At night when the key is in the house sitting on the kitchen table the attacker walks up and touches the door handle. The transceiver hears the cars call to the key, amplifies it, the key in the house hears the cars amplified signal and responds, the transceiver hears the faint response of the key and amplifies so the car can hear it. Door unlocks as car thinks the key is within range which is normally just a couple of feet. Some cars can be started using this method as well and only cease operating once the car is turned off. You can defeat this type of attack by keeping your key fob in a Faraday cage such as a purpose built container, and some have suggested using things like Microwave Ovens or refrigerators/freezers for the same effect.
