Accurate positioning technology review

I need a review of the state of the art of the technology related to the accurate positioning in a small area (about 2000 square meters). The case study is a car park, I need to know where a particular car has been parked; a nice solution would be having a low cost sensor or device to be put on every car and a portable device reader/finder that the car parking guy uses in order to easily find the right car. The scenario can be both indoor an outdoor, it would be better not to need infrastructure (antennas or power supply) in the parking.