I worked on a foveated video streaming system for 3D video back in 2008, and we used eye tracking and extrapolated a pretty simple motion vector for eyes and ig

I worked on a foveated video streaming system for 3D video back in 2008, and we used eye tracking and extrapolated a pretty simple motion vector for eyes and ignored saccades entirely. It worked well, you really don't notice the lower detail in the periphery and with a slightly over-sized high resolution focal area you can detect a change in gaze direction before the user's focus exits the high resolution area. Anyway that was ages ago and we did it with like three people, some duct tape and a GPU, so I expect that it should work really well on modern equipment if they've put the effort into it.