E.g. at the OS level, the pointer basically follows your gaze.
This summer I built a system that uses slight head movements for refinement, allowing hands free mousing as fast as a trackpad. However, eye trackers good enough for the system to be pleasant cost $10000+. I have ideas that would allow it to work with a $100 eye tracker, but even then it has the downside that the computer vision for your mouse will peg one core.
(Edit update: by "detectable" I mean theoretically detectable by a really good camera and software. In other words, it seems you are arguing the tech is impossible even theoretically due to some aspect of biology. Am I following you correctly there? Thanks)
Your field of vision (and focus) is much bigger than 1 degree, so any part of the image that you are "looking at" is something the brain is doing to the image as post processing, not something your eyeball is doing.
However! If you think outside the box, you might get a fairly accurate gaze tracker and a different GUI design to get this to work. That vision (no pun intended) is more of a long term one. An easy short term use for eye gaze use would be automatically setting GUI window focus based on eye gaze. That already might save you a keyboard-mouse switch. As long as you have no more than four windows on your screen, you can make it work with the current tech already.
And how about getting in the precision area like a finger has on a touchscreen?
You think, this is possible?
Because touch works pretty well, if the UI is good (big) enough ...
E.g. if the tracking is off (i.e. the predicted x,y coord differs from the target you had in mind with your gaze) I guess one would try to auto-correct the error by a slightly different gaze, i.e. looking slightly beneath the target. I am not sure if this is a problem or not?
We do not have this problem with the mouse, as we control it via relative speed and do not set specific x,c coords.
Maybe one could solve this by also tracking the head? E.g. make and educated guess via gaze tracking and let the user refine it with her ... nose. ;)