I just tried to find a link but have failed but, a few months ago, there was a video showing a camera-equipped quadcopter that autonomously tracked a water-skie

I just tried to find a link but have failed but, a few months ago, there was a video showing a camera-equipped quadcopter that autonomously tracked a water-skier. Not only was the flight path dictated by the course of the water-skier but the camera oriented continuously to frame the water-skier using a radio-beacon on the water-skier. The guy who built the rig had a tutorial site showing how he built the beacon and receiver. Beyond that, I haven't much insight into how such a platform would be built but, figuring that out is what the no-worries-about-money time would be spent.