You know that all GPS transmitters are in space, right? GPS is a unidirectional technology where GPS receivers don't (and can't) talk back to GPS satellites in any way.
If the caretaker wants to get the coordinates back, then you have to go through a server at some point. I think GP was thinking along the lines of something like Find My iPhone, where the GPS coordinates are sent to the cloud. You will need a mobile baseband radio alongside the GPS receiver.
Yeah, you are right of course. I was thinking of a GPS receiver with a mobile connection to send data to a central server, and it turned into ‘GPS transmitter’ :)