You guys are mixing up technology terms. GPS is receive only. Satellites send a time encoded signal. The GPS receives those and based on time differences detemine how far from a satellite it is. With 3 satellites you can triangulate a location on a map. With 4 satellites you can also get altitude.
So when a security system says it is a GPS system that means it uses GPS to determine location. It needs to use some other technology transmit that location. For example, rlink.com's security system uses T-Mobile's data cell service. FIN's FAQs say it uses a cell data service.
So with those system they will only work where there is cell data coverage on the carrier the product uses.
I've seen some interesting DIY systems. In ham radio there is something called APRS - a way to send data over ham. Here's a youtube video on the technology.
Commercial APRS GPS tracker.
Granted you do have to be a registered ham operator for those.
So when a security system says it is a GPS system that means it uses GPS to determine location. It needs to use some other technology transmit that location. For example, rlink.com's security system uses T-Mobile's data cell service. FIN's FAQs say it uses a cell data service.
So with those system they will only work where there is cell data coverage on the carrier the product uses.
I've seen some interesting DIY systems. In ham radio there is something called APRS - a way to send data over ham. Here's a youtube video on the technology.
Commercial APRS GPS tracker.
Granted you do have to be a registered ham operator for those.