about two years ago we were looking for a park at our local shopping centre and my boy says "you know what they should have? some sort of indication where the free carspots are. like so you can look down the row and know if there's free ones without having to drive up and down."
not sure if it existed back then, but today we went to the westfield at chatswood, and there's lights above each carspot, with a sensor, and the light is red when there's a car there, and green when there's not.
wish he'd done something with the idea and made us millions, but it's still an awesome improvement to the shopping experience!