Boris of Open Electronics wrote an article on his stand-alone access control with RFID project:
RFID Tags are increasingly used for many applications such as identifying objects by means of a code or access control. In logistics RFIDs allows asset tracking, or monitoring conveyor belts; in shops tags are often used as anti theft. RFIDs are also used for presence detection and security, with several use cases, for example in computer and appliance access and user identification. Due to the importance of RFIDs we propose today a simple, stand-alone project, which is basically a simple transponder enabled lock. This lock is equipped with a relay to be used to control an electric gate opener or a simple lamp.