##Introduction Assistive Context-Aware Toolkit (ACAT) is an open source platform developed at Intel Labs to enable people with motor neuron diseases and other disabilities to have full access to the capabilities and applications of their computers through very constrained interfaces suitable for their condition. More specifically, ACAT enables users to easily communicate with others through keyboard simulation, word prediction and speech synthesis. Users can perform a range of tasks such as editing, managing documents, navigating the Web and accessing emails. ACAT was originally developed by researchers at Intel Labs for Professor Stephen Hawking, through a very iterative design process over the course of three years. Professor Hawking was instrumental to the design process and was a key contributor to the project design and validation. After Intel deployed the system to Professor Hawking, we turned our attention to the larger community and continued to make ACAT more configurable to support a larger set of users with different conditions.