A method for providing human input to a computer which allows a user to interact with a display connected to the computer. A first target is placed on a first portion of the user's body, whereby an electro-optical sensor senses 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 are movable relative to each other. An output of the electro-optical sensor provides an input of a computer. The location of the first target and the location of the second portion of the user's body are then determined, and the output of the computer to the display based upon the determined locations are varied for contemporaneous viewing by the user.