This is interesting its a Tweeting cat door (pictured left) that has been made by a programmer to track his cats. The cats each have a RFID tag attached to their collars. When they go near the cat door the RFID reader reads the tag and if the cat is authorised a servo unlocks the cat door. Each time there is a cat door event a Twitter message is sent as well as a picture of the cat that has activated the flap. You can check out the updates at the following link.