Not that Great for Notice of IPhone left behind

I was looking for an app that would alert me when my iWatch series 2 was no longer connected to my iPhone - so I didnt leave my phone behind.

Unfortunately the implementation seems to rely on looking at Bluetooth signal strength and the app running on the phone to communicate with the watch. In any case fiddling with a sensitivity setting in the iPhone app can be frustrating and seems to fire unreliably when Bluetooth drops or is somehow interfered with even while you has a strong local wifi connection.

What I really want is a feature on the watch that warns when the phone connection for wifi and Bluetooth is dropped - and should not require a background app on the iPhone to be running to work.

GABATHEHUT about F-Secure Mobile Security, v4.4.9