So here's a problem: you want to allow your cat to get into your house whenever it wants, but you don't want to also let all the neighborhood cats come in as well, as they could do with a regular cat flap. The solution? Surgically embedding an RFID chip under the skin of your cat, of course.
That's how the SureFlap recognizes that the cat approaching is the one allowed inside. The RFID chip acts as a wireless key, opening the door for it when it gets close and locking up behind it. Sure, your cat probably won't enjoy going under the knife, but you'll enjoy not being surprised by a litter of some strange cat's kittens taking up residence in your kitchen.