Having witnessed many near-misses involving distracted drivers on cell phones, I want a mandatory system that detects an active cell phone call from within the vehicle and:

... immediately turns on 4-way hazard flashers

... activates voice prompt "Pull over! Pull over!" audible at both ends of conversation

... escalates audio prompt to the annoying "phone off hook" beeping after 15 seconds

... gives person at the wheel small zaps if vehicle is not in Park within 60 seconds (optional, but satisfying).