Protected Computer, Accessible Controls

"Guts" of computer not in the open

"Tower" or flat desktop, not laptop, under dash or in cabin
Components easily inserted into tower
Cheaper and easier to maintain/upgrade than laptop

Minimum space taken by controls

Display, keypad and trackball on dash can be weather-resistant
Cable comes through sealed grommet in dash or on bulkhead
Keyboard not necessary for most work

Another alternative

Purpose-built remote control for specific product