Cheap Touch Screen via Wii Remote
If this has been posted, I apologize, I haven't been here in ages and I am currently working on a setup using this technology and though it would benefit others, especially those on the low budget.
If this ever got big enough, the multitouch feature could be implemented into GUI development for car computer systems (forgot what the common name for these are around here); not sure how, but I'm sure developers could get creative. Either way, this is a great way to turn any laptop screen into a touch screen. The only thing the installer would have to worry about would be mounting and powering everything attached to the computer in the car.