What you saw there was my gaze 👀 My wife used some of those eye trackers for her research (which she finished a couple of years ago) so now I'm putting them to use while streaming:
https://gaming.tobii.com/product/eye-tracker-5/
They're a little creepy - I sometimes literally see tracker showing where I'll look next before I even think it. It's probably the closest that current consumer technology comes to mind reading