Seatbelts are an important safety device for maintaining control of your vehicle. A simple bump in the road can cause you to lose control by literally being bounced out of your seat. Granted it's only a slim possibility, but I've seen it happen to a friend of mine. It was funny to us at the time, but then we were out in a field.
So are they going to disable the police officer's computer while they are in motion?
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson