My brother's step-son had a stroke and now has locked-in syndrome, so I bought a Tobii 4C eye tracker for 160 Euros and wrote some software for Windows that lets you type using only your eyes and then speaks the text that was typed out.

You can download the installer here - Download the file iGazeInstaller.msi.

Of course this will only work if you have a Tobii 4C eye Tracker.

If the user is struggling with accuracy whilst operating, press the C key (to calibrate) and ask them to stare at each dot on the screen in turn (top left, then top right, followed by bottom right and bottom left).

I hope this brings someone the ability to talk again!

Note: I have no affiliation with the company Tobii at all, and the software is completely free.