Another physical measure–one that requires hardware on the fob side–is to disable unlocking when the fob is not moving. The idea is that when you’re sleeping and the fob is on your bedstand or wherever, the fob becomes inactive and impossible to relay. That at least stops the type of attack where thieves steal a car right from the owner’s driveway, using a high-gain directional antenna to pick up the fob’s signal and relaying it to the car.