Maybe an AM channel - like the Causeway uses - would be able to update people in realtime about the parking at given lots and direct them to the ones not filled. Or even use the KLSU station. Given so many with smartphones how about a Twitter feed or FaceBook page that can be updated in real time.
Problem is you're relying on the idiot cops and parking people to relay what they are seeing for this to work.
if the helicopters that ride around all day were giving info, then that would be more helpful.
regardless, sounds like a great idea.