This seems like a good idea, for keeping your cats safe if you do decide to let them go outside. Pretty expensive at the moment though.

Wonder if they will start doing it for humans soon

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Not sure how safe this actually is though, as obviously it would have to be a non breakable collar for you not to loose your cat. But is it is unbreakable, then this good have risks. What we want is some kind a chip that you can place under their skin, maybe with the microchip.

Great Idea all the same.