Follow me mode using madule or sensor?!!

Hi guys.
Have you seen the new drones with a follow me mode? I mean previous drones of dji followed the remote controller. (For sure new models use picture processing to follow)
I want to have a follow me in my new project. What madule or sensor or what ever do you belive i have to use, that lets arduno follows something like it's controller. Thanks.

GPS might work. Send the GPS coordinates from the controller to the drone and have it follow.

You might be able to put an ultra-sonic emitter on you or the controller and a ring or ultra-sonic receivers on the drone.

To be very good, it almost has to be image processing. The simplest would be to put a beacon on you or the controller that blinks a specific pattern. It still will involve a lot of image processing. A low end Arduino won't be able to do it. You need one of the ARM based Arduinos but it would probably be easier to use a Raspberry Pi. Lots of people are doing image processing there. I would start by looking at what the Open MV Guys are doing.