Found via ycombinator,
Itel has open-sourced the Assistive Context-Aware Toolkit software used by Stephen Hawking. ACAT was "developed in C# using .NET 4.5 and Visual Studio 2012 at Intel Labs to allow people with disabilities to communicate with ease". ACAT is operated using a single switch, which in the case of Hawking is a facial signal (cheek movement) interacting with an infrared beam. While the ACAT system provides effective communication assistance, it can do a lot more; its powerful menu-based UI allows for control of the entire operating system.
Story here [msdn.com]