You also get a Bluetooth disconnection reminder feature that sends you an alert when the watch gets disconnected from your phone. It can potentially prevent you from forgetting your phone. Here’s how to use it:
Step 1: Swipe up on the home screen and go to Settings.
Step 2: Scroll down and click on the Bluetooth option.
Step 3: Enable the Disconnection reminder. Now, it will tell you when the watch is disconnected from your phone.
Source : wearablestouse.com