It would have to apply to all vehicles because any new vehicle which enforced either would be unmarketable to a large number of people. Honestly, as much as I hate the idea, I do like the fact that the value of my non-nanny vehicles would likely increase if such a thing were to be mandated in new vehicles.
The likely truth is that any attempt at gov't enforcement of driving behavior at this level would immediately result in the politicians suggesting it losing their job. Maybe in Europe it would fly (I'm not convinced, though), but in the USA definitely not.
