What it is:
Dasher is an information-efficient text-entry interface, driven by
natural continuous pointing gestures. Dasher is a competitive
text-entry system wherever a full-size keyboard cannot be used – for
* when operating a computer one-handed, by joystick, touchscreen,
trackball, or mouse;
* when operating a computer with zero hands (i.e., by head-mouse
or by eyetracker);
* on a palmtop computer;
* on a wearable computer.
The eyetracking version of Dasher allows an experienced user to write
text as fast as normal handwriting – 29 words per minute; using a
mouse, experienced users can write at 39 words per minute.
To know more about:
sudo apt-get install dasher