You can relatively easily set up an amplifier with a directional antenna. Also, that will easily false positive - there are a lot of things that reflect RF in weird ways.
A lot of things will reflect RF in weird ways, and that is precisely what I was counting on. Surely an amplifier that changes the detection range from 1 feet to 100 feet will be emitting much much higher energy than what is usually experienced under normal operation. I guess, the antenna does not have to be omnidirectional as long as the attacker can search around the direction the key is likely to be.
