Roger is a tool to allow the extremely disabled to type with a single button or switch. This means that in principle any muscle with reliable voluntary control can be used to enter text, for example by using a foot pedal, tilt switch, bite switch, tongue switch or sound-operated switch.
The interface, accessed through a web browser, is a type of scanning keyboard: different areas are highlighted in sequence, and the user activates their switch/button at the appropriate time to narrow down on the key they wish to press. A predictive text model (trained on a hundred million words of text) attempts to provide intelligent suggestions. Most words can in practice be typed with 5-10 presses of the switch/button.
The current development version’s source code (working, tested on a few systems, but undocumented) can be downloaded from the roger github repository.