While you're at that site, also check out this:

http://www.thecompassstore.com/v2000.html

My wife had bought me one for my truck and it worked VERY well. Very easy to calibrate and the batteries lasted much longer than I expected. If you're handy I'm pretty sure the same company makes a version that can be hard-wired into your vehicle so that it draws power from the vehicle and even lights up.