I agree with Boomslang. It should be technically possible (in fact, it is: similar systems have been built before) but for driving a vehicle? I hope nothing like that is ever used on any road I'm likely to be on. Making it safe would seem to be very hard to do.
How would you handle those little involuntary glances which everybody does from time to time? And even using a heads-up display, how would the system tell the difference between the user looking at something on the road and trying to trigger a command?
Torben