Vaporware: Smart Pet Door
Most veterinarians now offer a service to embed RFID chips in our pets. These chips are inserted just under the pet's skin and uniquely identifies that pet even if the collar is lost. So far this chip is only used at vet offices and some animal shelters to reunite lost animals with their owners.
This idea is to build magnetic pet doors that are normally locked with a strong magnet until the pet's unique RFID chip comes into range. The pet may freely enter and exit the pet door without restrictions, but all other animals only find a solidly locked door.
Since the door would require access to electricity, extra features could be available such as time-based access and activity tracking including foreign RFID signals.