GPS would have helped when the Burglar broke into my house and wasn't kind enough to close the back door they bashed in on the way back out.
My scared cat stayed inside, my 2 dogs also stuck around (the thieves did close the front door on the way out.) But my adventurous cat decided to take a walk. We had signs up, every shelter contacted. Our kitty has an ID Chip so if someone picked her up and take her to a vet we'd be okay.
Thankfully 2 weeks later she was meowing on our front porch to be let back in (guess all the tuna bait helped.)
If I had a small GPS locator I would have found her that first day, probably very close to where we were already looking.