Hey, I just found something really cool!
It's called "KeyCounter" but that's not really a very accurate name. Basically, it's an encoded keyfob starter disable device!
The antenna is by the ignition switch, and if it detects a valid keyfob when you turn the key, you can start the car. Otherwise you can't!
This looks really cool because it doesn't require any remote controls or anything.
The page for it is
HERE