Download GazeFocus

Installing

Open the disk imageDrag GazeFocus into your Applications folder.
Open it the first timeRight-click the app and choose Open, then confirm. See the note below on why.
Work through setupCamera, Accessibility, then calibration. About two minutes.

macOS will warn you on first launch.

GazeFocus isn't signed with a paid Apple Developer certificate, so Gatekeeper shows “GazeFocus cannot be opened because the developer cannot be verified.” This is expected. Right-click the app in Applications, choose Open, and click Open in the dialog. You only do this once.

If the dialog won't let you through, go to System Settings › Privacy & Security and click Open Anyway.

The two permissions it asks for

Camera

Used to read the position of your head. Frames are processed on your Mac by Apple's Vision framework and discarded immediately — never written to disk, never uploaded. The app has no network entitlement at all.

Accessibility

Required to move keyboard focus between other applications' windows. There is no other API on macOS that can do this. macOS will send you to System Settings › Privacy & Security › Accessibility to tick the box.

Uninstalling

Quit from the menu bar, drag the app to the Trash, and delete ~/Library/Application Support/GazeFocus if you want the calibration data gone too. Nothing else is left behind.