Unfortunately, I do not see this happening. Xbox programs are specially written to run on the xbox. However, you could always load Linux and run something like VMWare (I think that's its name) so you can run Windows programs. I don't know how well the hardware is going to play with the software and highly doubt you'll be able to get GPS and a touchscreen to work.
If you want to run an Xbox in the car and have a front-end, I suggest running Xbox Media Center and use a wireless RF xbox controller for the interface. It'll give you music, videos, and DVD with very little fuss.