I am positively surprised by Eye Tracker 5, but it takes a lot of time and patience to set it up correctly. I have even used and tested it for Arma 2 and Arma 3. That is, infantry, vehicles, helicopters, aircraft. In the meantime, however, I bought a new monitor that is italic and I have to tinker with something so that I can put it back into operation.
The thing recognises eye movements and head movement, both can be adjusted independently.
It's important not to be too close to the monitor.