I wonder what the accuracy is if you drop the eye tracking and only do head tracking on that demo.
I don’t think eye tracking alone would give you the necessary bounds for inferring the keyboard size. For one, eyes flit around more and also are harder to see.
I also wonder how easily this attack is foiled by different key clusters. E.g it looks like they’re relying on large head movements at opposite ends of the keyboard to infer the bounds.
But keyboard use can be very clustered which would foil the ability to know how wide the user has the keyboard.
I imagine it also breaks when the user moves the keyboard