I wonder if this bluetooth trackball would work well with a carputer?
http://us.gizmodo.com/gadgets/periph...all-138514.php
Basically use the vga-out cable to the touchscreen, and then mount the trackball on the centre cosole somewhere to controll a pointer ont he screen. I believe WM5 has generic pointer capablity doesn't it? Heck, you wouldn't even need a touch screen for this to work. You could use any car monitor & pop a vga to composite converter in behind it.