Each person can have a primary device assigned to their Profile. That primary device's connections and disconnections from the network determine whether the person is home or away. Motion alerts will only be sent when enabled if no primary devices are at home.
You should always choose a primary device that people are not likely to leave home without and will always stay powered. Smartwatches that connect to WiFi or mobile phones are ideal for primary devices.
Assigning a primary device
Before assigning a primary device to a person, they must already have devices assigned to them.
Navigate to the Person you wish to edit.
Tap on their portrait to bring up the options menu.
Choose the Assign primary device option.
If the person already has a primary device assigned, choose the Edit primary device option to change it.
Swipe through their assigned devices, and once the desired device is found, tap on the Assign as primary button.