The two I've seen that work on the cats' own ID chips are PetPorte and Sureflap. I think PetPorte have been bought by Staywell now. We went for a Sureflap because the PetPorte has a ruddy great lump sticking out of it that houses the sensor etc, and also because it is primarily mains operated (albeit with battery backup), and I didn't fancy having a cable trailing from the door to a wallwart. The Sureflap is battery operated, and I've been extremely happy with it. The batteries seem to last close to a year (4 x AA, I usually use Maplin's ones), and that is with 3 cats who all go in and out quite frequently. The wind can't blow it open because of the sensor operated catch, however I have noticed once or twice that if the cat enters very slowly, and their tail cushions the drop of the door, it doesn't have enough mass to go past the catch and close properly.