A long time ago there were cars with the shoulder belt attached to a motorized track on the door frame that would pretty much force you to wear it...only for the front seats though.
Maybe instead of a power button, cars should turn on when you buckle up after the brake pedal is depressed.
They tried that with a few models and no they shouldn't. It was an actual pain and prone to failure. I had to rewire my friend's car (an all the time seat belt wearer) because of how crappy those things hold up.
People will wear them or not. Making things more complex just means it will fail and make people do strange things.
It should when it was tried and is just not a working concept. It basically comes in the same category as "bike handle bar warmers". Making an annoying ding is going to get most people to put on their belt. Making the car not move is one more thing that can go wrong in daily life and can make an emergency worse.
Maybe instead of a power button, cars should turn on when you buckle up after the brake pedal is depressed.