Behold the PetsMobility PetCell (justifiably sceptical review by Gizmodo):
The PetsMobility PetCell is only a concept for now, but the patent-pending collar could be great — if you don't mind spending a lot of extra cash on your pets. The idea is simple: it's a cell phone and GPS unit on a collar, with its own private number. Using caller ID, it automatically picks up when an approved number calls, allowing you to speak to your dog or cat (but probably dog) from wherever you are. And with the GPS service enabled, you'll even be able to yell at them when they've wandered too far from home.
Ignoring for a moment the ridiculous concept of equipping your pet with a mobile phone, just how badly would this freak out your little non-human companion? Rover or Fluffy is out and about, happily doing doggy or catty things, when suddenly, your disembodied voice comes from the region of its neck. It knows darn well that you're nowhere near, as it can't smell you. My guess is that it (and the expensive PetsMobility PetCell) would disappear over the horizon in a cloud of dust, never to be seen again.