I've been so happy with Torque, that I decided to keep using it instead of building an MPGuino or similar. In fact, I decided to go out an by an inexpensive 7" tablet to install permanently in the car. The tablet I chose was an Acer Iconia One B1-780, which I picked up for $110 at Walmart.
I'll post some pictures once I've installed it, but in the mean time, here's a screenshot of the layout I've come up with:
I have a darker version that kicks in at night.
I'll be using this primarily to run Torque, but also MapFactor Navigator (a great free off-line GPS app), and RocketPlayer (a music player app). I'm going to install it in place of my car stereo (the radio doesn't work anyway), and put in a small home-made amp to drive the speakers.