One massive problem with scarce parking and no smart system to distribute it is that a lot of vehicles spend a lot of time driving in circles looking/waiting for a spot to turn over. If there were a system that was essentially a free lottery, it could avoid a lot of wasted time and pollution. You'd have to incentivize the occupant somehow though.
something like this:
1. Occupant is about to leave and sends an alert of near term availability.
2. N subscribers get the alert and enter the lottery, lottery executes, winner is selected, and winner is notified that they get the spot, no charge. The lottery could be weighted by karma, say the number of times that lottery participant has yielded a spot to others.
3. Occupant yields their spot to winner, and receives parking karma for next lotto.
4. Society benefits by less traffic, pollution.