That wiring should be extended to small, bright (~mini-strobe) lights on the outside of the car, just above the driver or passenger side doors. Driving when not belted-in would turn the lights on, drawing the attention of law enforcement.
Or maybe the wiring could be attached to the turn-signal switch, so all four lights, two front and two back, would blink if the belts were not fastened. [Not the best alternative. Anyone have a better idea?]
Either way, the drivers (and passengers) would know they should use the seat belts or they would stand out in traffic as non-compliant scoff-laws.
