Whistle 3 device uses a few different types of technology, including GPS. The Whistle 3 device uses GPS and assisted GPS to keep track of your pet's location. GPS locations are acquired by using triangulation using the Global Positioning System. Assisted GPS is when the device uses a cellular network's cell towers to triangulate your pet's location. Once the device has this location, it delivers that location over America's largest cellular network so that you can be notified.