Making a car difficult to steal

Still toying with ideas here. Got my dash harness out chasing some electrical gremlins so it seems like a good time to do something.

Anybody have any ideas for a remote relay of some sort? Something you could activate with a fob, or even better would sense the proximity of the fob? Kind of coming up blank on my searches.

Thought about hidden button, but seems like that depends on the guy not finding it. Kind of like something a little tougher to defeat.