- The "I haven't used my turn signal in five years" signal. This warns me that the driver is likely to merge into my lane without warning.
- The "coffee cup in use" indicator, hooked up to the driver's side cup holder, turns on for five seconds after the cup has been removed from the holder, to warn me to watch out for violent swerves due to hot liquid spills.
- The "child in car" light turns on when the child seat is occupied (clearly this requires modified child seats with radio signals and weight detectors). Now I know if the parent is likely to weave back and forth as they reach back and try to pick up the needed toy.
- The "music volume" indicator tells me if the driver is likely to be listening to overly loud music and have their foot too heavy on the pedal -- and unable to hear me honk.
Clearly these indicators would improve public safety, and since we know there's no cost too high to save a child's life I expect these improvements will be adopted immediately.