What matters on a collar
Weight and waterproofing come first. A tracker heavy enough to annoy a cat will be off within a week, and any dog that swims or works in wet grass needs a properly sealed unit rather than a splash-resistant one.
After that it is the trade-off between battery life and update frequency. A tracker reporting every few seconds gives you a live trail but needs charging every couple of days. One reporting every few minutes runs for a week or more and is usually enough to find an animal that has wandered. Geofence alerts matter more than either. Knowing immediately that they have left the property is what keeps the search short.
Related
For a tracker on the vehicle rather than the animal, see car GPS trackers. For a person, see personal GPS trackers.
Common questions
Does it work in rural areas? It needs mobile coverage to report. Check coverage where you live, particularly in valleys and dense bush.
How often do I charge it? Two days to two weeks depending on reporting frequency.