electronic cat flap (Lutana)

this is the same size as a standard cat flap that goes in a door, but it has electronic controls so that you can set it for times that your cat/cats can or cannot use the door. It runs off batteries so doesn't have to be wired in. You set it using your cat's microchip, that's what it recognises. and its very sturdy, so neighbourhood cats won't be able to get in (apparently its raccoon proof).