I saw the movie "Over The Hedge". There was a dog that had a collar that
would activate a doggie door that only a critter with the collar, and maybe
a critter tagging along with it, could pass through, then it would lock
again. I haven't seen such a device. Are there such things? And if so, do
they work? Anyone that has used these, if you might chime in? Thanks.

--
Brian