There is home again and avid. Both are microchips for pets. I have some that have home again in them and the others have avid in them. It depends on what chips your vet uses. Neither of the chips are GPS chips, only identification chips. This is the link for Home Again
HomeAgain and this one is for Avid
Microchip ID, Identification Systems for Animals
My vet scans every new dog that comes into the clinic the first time to see if there is a chip, but once he knows you and gets to know your dogs, he only scans when you bring a new one in that is older.