Microsoft has filed patent for an eye tracking keyboard which would be able to track eye movement. Previously we have seen similar technology being used in Samsung Galaxy S4 where a sensor could detect the eye movement of the user and stopped playing video when the user moved his eye away from the user. Similarly this eye-tracking virtual keyboard will bring a shift in the way we input text on computers and mobile devices. The most promising utility is its compatibility and friendly approach for people who are not able to use keyboards with hands. But generally the idea arose from the fact that typing was till date confined within physical and virtual keyboard or on-screen keyboard which required physical touch.
According to the description of the patent,
In a computing device comprising a data-holding subsystem and logic subsystem, a method, comprising: receiving a data set comprising a plurality of gaze samples, each gaze sample comprising a gaze location and a corresponding point in time; processing the plurality of gaze samples to determine one or more likely terms represented by the data set by comparing the plurality of gaze samples to a layout of user input keys displayed on a display, and based on overlapping user input key and gaze locations and a length of time spent gazing at each user input key, assigning a per-key score to each user input key for each point in time; and providing the one or more likely terms to a display device for display.
So when you are looking at the newly invented virtual keyboard, the sensors will track your eye movement from one key to another and measure the angle of shift. This angle will be matched with some reference which will then help the keyboard to understand what key you are thinking to tap.
Source: UPSTO PATENT