This site uses side-to-side eye movements to operate a simple typewriter.
The typewriter needs a webcam, a well-lit room, and a wide enough screen that the camera can see when your eyes turn from one side to the other.
Laptops work, even cheap ones if they are newer. Tablets can work too if they are optimized for landscape mode. (e.g. iPad Pro, tablets with a camera on the long edge)
Current versions of Chrome, Firefox, Safari and Edge are all compatible.