In order to receive a notification as soon as the wearable realizes that you have not been moving for a while (60 minutes), you have to switch on the Idle Notifications. First access the drawer menu by swiping from the left to the right within the main-screen or by tapping the menu button in the top left corner.
Now choose the option “Wearables". Select "Idle Notifications" to toggle notifications on or off.
Now scroll to the bottom of the page, where you will find the idle notification settings. You can also set a time frame in which the notifications will be triggered.