FWIW, there's an iOS app called 'Autopilot' that does it for the P2V+. Kind of expensive (as far as apps go), but perhaps they'll be able to quickly port it to the P3.
The Phantom 3 does not have "follow me mode", nor does it have " waypoint mode" which I like to use. I would have at least liked to have one or the other, but I guess DJI is not Burger King, so we can't have it our way!