By fitting a GPS tracking device to an animal's collar, you can monitor its location and past trails on a map, showing where it has been.  
There are options to be sent alert messages if it enters of leaves particular places.

Pouch:  Pet trackers can attach to a collar or saddle of any animal.
Trackers are water-resistant rather than completely immersible in a liquid to a depth for a lengthy period.
Trackers can function even in challenging environmental conditions while remaining light-weight without limiting an animal's behaviour.  

Potential uses: There is an unlimited number of possible uses.  Here are a few:

1) By tracking the past movements of a dog can be viewed. When a tracker is attached to a collar, it can established whether or not your dog is worrying sheep or other farm animals, which is a growing scourge for Farmers;
2) Can be used In races/competitions, to show the current position and ranking of competing animals;
3) It can confirm the passage of a horse and rider around Map Checkpoints in remote unmanned locations;
4) Horse eventing: Combined with 10 second position reporting, a tracker provides an accurate record of speed & distance stats of competitors;
5) Discover where your cat is getting fed!

The tracker is approximately the size and weight of a matchbox, and so will not be a burden to most animals.