What do you mean by face tracking? Never heard of that. What applications use it? Genuinely curious.
Mostly simulators. Tracks your face by various means, webcam, IR, etc. When your head moves your camera moves.
Interesting! So a flight sim which changes your view or what application would do this? Maybe thats something we can get working in linux?
I think I heard of them being used in Arma/Milsims so you can turn your head slightly left or right, so your character looks to their left and right on monitor.
Thats pretty interesting! Sounds like a niche enough thing that would need specific attention to get working.