Terrible app
This app actually doesnt do what is says. It only disable the auto-join on your wifi networks. For example, if you have two SSIDs at your home, youre able to disable auto join feature in one of them, so the other will be the "preferred". But if youre in a room where the preferred wifi is out of range, youll have to connect to the second WiFi manually. It does the complete opposite of the program suggests.
RafeNunes about
WiFi Priority