Yes, thank you. I have been searching for an app that does this since my S0. So happy to try this one. the app Lookout had this feature for while, but they pulled this feature and it never really worked. I agree that it has been baffling that this was built in to the Watch Os from the beginning. Apple may finally come out with Tags, and they may do some tracking like this, but it isn't clear in those rumors if the Apple watch is even part of their plan.
I did some initial testing, and this app may work; it notifies after 1 min of separation, which is a really good default setting (Lookout would notify when it thought the connection was about to be lost, so went off all the time, even inside the house). I did turn down notifications to "less" since when outside I drop in and out of connection, and I don't really want this going off repeatedly. There really isn't any documentation or explanation of how this app works though, so this will be a learning process. On the developers facebook page, he claims there is some form of machine learning so that it learns your habits and goes off less (we shall see, here at home).