If you haven't heard about the Tagg GPS dog tracking system yet, this video explains it very well. At the 2015 Consumer Electronics Show the original system was on display along with the Tagg GPS Plus, the company's second generation device.
Tagg monitors not only keep you aware of the location of your pet at all times, they also monitor your dog's activity level, and the new system can also track the temperature of the environment your dog is in to give you updates when the temperature gets too hot or too cold.
The Tagg tracker stores weeks of information on your pet so you can monitor any developing health trends. It also has the longest battery life of any dog tracker, lasting over 15 days before it needs to be recharged.