You could try building it yourself. I recomend a servo motor connected to a latch that can actuate to stop the door opening. Hook it up to an xBee module for rf, pots Italy with a microcontroller in between, or glue logic if you prefer, and you are done. The one other thing I strongly recommend is installing an emergency override that can open the door reliably without using any electrical components, so in the event of the system failing you don't risk being locked out.
