When I became involved in lost dogs I researched and even posted about some of these trackers.
Whistle is only recommended for pets over 15 pounds. It seems to have a lot of issues of late and if you have more than one pet.. could get costly.
I know of people who have three cats, a couple of cats and a couple of dogs.
It won't work for cats unless they are big...
The cost of the device is $80.00 and the people writing the review are saying the cost of the service is $10.00 a month.
Some of the reviews said it gave them false readings, telling them their pets were out of the zone when they weren't and some said it gave them false reading as to where their pets were.
For me. I feel I will wait until they get the kinks out.
If you have pets over 15 pounds and can afford for all of your pets! YAY!!!! You hit the jackpot!!
I'm still looking for something for my guys, that isn't going to cost me just to monitor that gets better reviews.
Here is a link to the product. I hope it works for you! It's a GREAT idea!
Amazon.com : Whistle GPS Pet Tracker : Whistle : Pet Supplies