[rjvs]

What about SMI already tracking pupils at 250Hz? https://www.youtube.com/watch?v=Qq09BTmjzRs That tech is still expensive and I don't know how accurate or reliable but if it is good enough for foveated rendering, I would have expected it to be good enough for focus as well. Care to elaborate as to why it wouldn't work, or is it just beyond your horizon of "today"?

[modeless]

It's not accurate or reliable enough (in addition to being very far from a consumer price point). Reliability in particular is difficult to assess and usually lacking in eye tracking systems. Also just because the cameras are running at 250 Hz doesn't mean the latency is 1/250 seconds or even close to that.