I've been keen on doing a carputer of sorts myself, but again, alas, with MN temp ranges, I fear it would fry most all the off the shelf stuff. The other issue is visability. I have a stack of old Crackberrys that have ideal screens for the environment (work in direct sunlight) But the units themselves are not really hackable (old OS/ can't get at any of the I/O) Have not seen anything on using the screens either.
I figured I would just start with the wireless entry via bluetooth and work up from there. There is a cut off point when there is more hardware in the car than the vehicle itself is worth.