Firstly, I would like to commend you for your awesome show! I started watching when Hak5 on Revision3 had plugged your show, and I have to say, I am addicted to it!
From watching the first 2 episodes, I had come up with some ideas of my own. One would be to create a Car PC system. Many manufacturers offer a touchscreen system that can give you GPS and a built in media player, but charge about $1000 for the option! I know there has to be a cheaper way involving a touchscreen netbook, and it could offer even more features than the standard touchscreen package(it is simple enough to build or buy an interface that will let you control relays that already operate things like headlights, starter, locks, windows, etc.). It also would be easy to take the webcam from the netbook lid, and move it to the back of the car to use as a backup camera too.
The possibilities would be endless, and I think it would make for an awesome episode!