Microchips in dogs and cats only work whent hey are read by a scanner placed over the animal. If the dog is found by a dog warden, or taken to a vet or rescue organisation they should (notice I say 'should') be scanned and the details of the owner can then be traced because they are kept on a database. Therefore it is important if you move (or even if you go on holiday) to let the database people know (most are with Petlog). I would think that to implant a satellite tracking device in an animal would be very costly and probably too big to go under the skin like a microchip does.
Dog theft is indeed on the increase, visit
http://www.doglost.co.uk to see just how many go missing every day. Not all stolen, but many are, only this week an elderly owner has had a Newfoundland cross stolen after leaving it outside a supermarket near Wigan. Please don't leave your dog in a supermarket car park or tied up outside a shop, people are nicking them and either claiming a reward, or selling them on in pubs etc.