The invention provides a method for providing human input to a computer which allows a user to interact with a display connected to the computer. The method includes the steps of placing a first target on a first portion of the user's body, using an electro-optical sensing means, sensing data related to the location of the first target and data related to the location of a second portion of the user's body, the first and second portions of the user's body being movable relative to each other, providing an output of the electro-optical sensing means to the input of the computer, determining the location of the first target and the location of the second portion of the user's body, and varying the output of the computer to the display based upon the determined locations for contemporaneous viewing by the user.