Surely someone somewhere will bring to bear a solution that will disable all but voice calls on smartphones while the smartphone is paired to the car and the car is moving but allow for the devices of minors in a moving vehicle to still function like smartphones. They might also use interior cameras to ascertain who is driving and which device should be neutered but for emergency communication.

Yes, people would be annoyed at first but they also will experience a sigh of relief that they don't have to reply to a boss's or co-worker's text in the middle of a commute or running deliveries, etc.