An overview of technology used to establish communication between a human and a computer was provided, trough history and in the modern age, with the purpose of showing the progress in this type of technology. Different systems and ways of communication that they provide was shown. Focus was made on eye tracking technology, types of devices for gaze and eye detection, ways that each of these devices measures gaze and eye rotation and the way they work. Special mention was given to the application of eye tracking systems in assistive technology. A short overview was given explaining the types of users that benefit the most from this technology and the states that afflict them causing limitations in motor functions and communication. Also an overview of a few of the currently available eye tracking devices was given. Examples were given of devices form Tobii, IrisBond and EyeTech companies. Examples were given of devices and the technology behind them for each of the business units that make the Tobii group. Also, examples of devices and technology from IrisBond and EyeTech were given. Short instructions were given on starting with implementing eye tracking into applications. The process of implementing eye tracking into applications running on Windows was given, as well as for those using the Stream Engine API or the Interactive Library made by the Tobii company. A simple simulation of a system using eye tracking for control was made in form of a game intended for kids with limitations in motor functions and communication, for the first four grades of elementary school. Technology used to build the application was mentioned, description of application behavior and appearance was given, and the method of simulating an eye tracking system was explained