One critter doggie door?

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
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Brian O wrote:

It was a cat. But look at this: http://www.petsafestore.com/stinelpetdog.html Yes, they work.
--
Grandpa
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In typed:

Hmm, intersting. It's infrared though; too bad they don't make one using a radio signal - more reliable less prone to dirt/fur messing it up.
Any further sources?
Pop`
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typed:

http://www.drsfostersmith.com / Nice company.
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Pop wrote:

How about an ultrasonic activated Star Trek style? http://www.hitecpet.com/powerpetdoors.html
You can Google for others on your time.
--
Grandpa

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Google, Automatic Doggy Door
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On Fri, 21 Jul 2006 18:41:51 -0500, snipped-for-privacy@webtv.net (m Ransley) wrote:

Or "electronic dog door"
tom @ www.FindMeShelter.com
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