Some of the guys over on
www.ffoc.co.uk have an in-car computer installed into the dashboard. Stevie-G (
http://www.stevieg.org/carpc/) is one person who's done it particularly well and documented the process to some extent for others who want to put a fully-functional pc into their car.
Considering that a car is most people's largest expense, next to a house, it's only fitting that it should fit the bill.