Or just chip your pet with a sub-dermal chip.

Yeah, the subdermal chip is a good idea in case your pet gets lots -- mine has one. But if it were RFID-compatible, that would be even better, as it really opens the field for innovation in consumer products.

Of course, there are still privacy concerns even with this, since if your pet's movements can be tracked, and your pet doesn't happen to be lost, that implies that YOUR movements can be tracked as well. It's easy to get lost in tinfoil hat territory with RFID, but there are some serious privacy ramifications that need, NEED to be addressed.

Anyway, I like the RFID-enabled doggy door, since it would be more secure. Our dog is so big that a skinny human could wriggle in through ours. Not anymore if it were keyed to his RFID tag.

The food dispenser could be smart enough to dole out different amounts of food depending on which of your dogs was there asking for it... that kind of thing... but I don't really approve much of automated food dispensers as it is. I think they break a very important part of the dog-human bond.

Other ideas -- with RFID you could get notified immediately if your pet runs away (just need a way to screen out false positives, like when it's you talking Fido for a walk yourself!). Your pet store and veterinary office could have a treat dispenser that automatically dispenses your dog's favorite treat when you walk in the door.

The RFID tag could also enable definite proof of an aminal's vaccinations. And just imagine if your female dog (sorry, I just can't use the correct word) winds up pregnant, and you can access a log file to discover who the father is!

Lookee here, this company sells what you are looking for....

http://www.iautomate.com/dog_collar.html