Wi-Fi serves a couple of very important functions for Whistle 3.
First it allows the Whistle device to communicate with the app on your smartphone to relay activity and other important information about your pet. In addition to being the gateway for communication from the tracker, Wi-Fi also let's the tracker know when your pet is in a previously setup place. When the tracker detects your Wi-Fi network, it knows that your pet is in a safe place and can switch to power save mode to use less battery power. In power save mode, the device's communications and functions are limited to just the basics, which significantly extends the Whistle's battery life.