You've unlocked a memory. Probably 10-15 years ago, I tried a bunch of eye tracking apps and found one that somehow worked really well with my cheap USB webcam. I'm sure it needed to be calibrated first. It was classic developer software, snappy with bare-bones UI. Freeware, ran on Windows 2000, not sure if open source.

I wonder if I have it backed up or could track down what it was again. I was not much of a developer then, but these days it would be simple to wire up simulated mouse events.