The driver would see on-screen directions to the parking space (with content provided wirelessly from the parking lot computer), and warnings if the car is not being parked in the correct space.
Sensors would be needed in each space (e.g. magnetic field) to determine whether the space is occupied.
Such a system could also be linked with the billing function to charge drivers exactly proportional to their stay length.
Disabled drivers would need to be routed to the disabled spaces.