Whistle GPS Pet Tracker Find lost pets quickly - Whistle GPS notifies you if your pet ever roams from their Whistle zone, a customizable safe area you designate for your home or office, and allows you totrack their location directly from your smartphone. Nationwide coverage - Whistle uses cellular and GPS technology totrackyour dog's location anywhere you get cell service in the U.S. On-demand alerts - receive notifications via app and text alerts when your pet gets out Keep them healthy - Track your dog's activity and rest for key insights about their behavior and health. Durable + Waterproof - designed to go anywhere with your pet. Whistle GPS is recommended for pets 15 lbs and above Whistle GPS Pet Tracker attaches to any collar or harness up to 1'' wide. Whistle GPS Pet Tracker requires a service planfor cellular connection,as low as $6.95/mo to be selected at activation