I bought a pawtrax GPS tracker in August this year as was moving for third time in same year, near a v busy road & wanted reassurance that i'd be able to find my easily spooked but (then) outdoor loving cat.
I found it worked very well when it worked, mixed bag really as mine went & hid in some urban woodland nearly a mile away where i never would have thought to look. I say mixed bag as the unit stops responding when blocked by trees.
It did send back a link eventually which allowed me to track my boy & walk him home but still undecided if the hours out of range caused more worry than if he'd not been wearing a gps collar at all.
I did love being able to text the cat whenever i wanted an idea of where he was & i did use it briefly when we first got to fourth (& final) home which was re-assuring.
Never did manage to work out the on-line tracking platform & main complaint is that the collar stopped charging so is useless now.
Customer service support was fantastic via facebook though & the inventor of pawtrax has now launched the 'halo' model which looks a lot thinner & more streamlined than the version i have (box is a bit heavy & 'clunky' on that one but never bothered the cat to wear it)