Parking Timestamp

On every vehicle equip a Timestamp that automatically records the time as soon as the vehicle is shifted into Park. Upon shifting out of Park, the Timestamp is cleared. The is not displayed, rather a police officer must retrieve the time with a little RFI doohickey, something that is only available to the police. This way, when a vehicle is blocked in on a city street, all the offended party must do is call the police. When the officer arrives, he need only scan the car that is blocked in and the two cars to either side of it to determine who was there first. This allows him to determine who gets the ticket.

The city would be quick to respond to such calls, as the greedy coppers are always eager to exceed their quotas, so you need not wait long. In fact, I imagine a portion of the ticket (like a ticket stub at a theater) would be handed to the offended party as an irrefutable excuse for being late to wherever it is you were wanting to go. Employers and professors would be prohibited from administering punishments for tardiness if presented with one of these, and doctors would have to make room for your appointment when you arrive, provided you call them beofre you're appointment time to let them know ahead. The doctor could be reimbursed for his time by the offending driver.