The other possibility would be to have a laptop in the car, but the models I have at my disposal are just:

a) too large in size to have 'in car' in general,
b) run out of batteries at some point,
c) look rather hilarious sitting on the front panel (eat half of the windscreen visibility = probably illegal),
d) could be seated on the passenger's seat, but yet again not a good solution
e) attract thieves too much.