Sweet, well done so far! As long as it works in Windows and can use a picture of my truck, I'm definitely one to support your project! Well level mounting shouldn't be necessary if you have a centering feature that will use it's existing position as center. Getting a perfectly level mounting in a vehicle can be almost impossible. Awesome if you'd get atmospheric pressure too! I don't need a compass since my truck has one, but I would still use that feature, and I'm sure others would however. Since you'd be the first, there could be a market for such software+device.
I've seen the Rad-1 many years ago, but it's big and ugly for what it does. I want to use the CarPC since it's already there, and not have another piece of something mounted in the truck; keep it clean and simple, the less **** the better.