This is pretty good and can follow closer and lower than the P3 follow mode.
A good contrast subject is helpful.
At one point I set it to circle but went too fast and it lost me.
If it does lose you it just stops but will sometimes re-acquire and start again unaided.

This is also available on Phantom 4 I believe.
A very useful tool for recording farm activity - while you are doing it - as once set up you can just keep an eye on the phone screen and record a couple of minutes to use later with other material.
If things go wrong pause or stop on the controller cancel the auto mode and it will just hover.
You can change altitude or distance away and gimbal tilt during the active track recording. 

On a slope you have to watch it as the mode to follow terrain can't be combined with the other active track options such as Profile (alongside).

https://www.youtube.com/watch?v=S5xhyNylRdI