A 3D cursor or joystick device and control method employs a complementary pair of emitter/detector units, one worn on a part of a user's body (e.g., the head) and the other mounted in a stationary position on a display monitor facing the user. Each unit has an array of photovoltaic (PV) cells centered on a normal axis and an infrared diode for emitting a light beam on the normal axis. Each photodetectors array receives the infrared beam from the other unit and provides output signals representing the light intensities of the received beam on the PV cells. The PV cell response signals of the complementary units are used together to calculate the position and angular orientation of the user-worn unit relative to the stationary unit. The position and angle values are used by a software device driver installed on a computer to control 3D navigation functions of the associated application program on the computer. The system can be used for playing interctive 3D games, and also used for hands-free control in a wide range of other applications and environments, such as to control flight motions in a simulator or cockpit of an aircraft, or the command center of a naval vessel, spaceship, land vehicle, etc., for disabled persons to provide hands-free input to a computer, motorized wheelchair, prosthetic device, etc., and for controlling various functions in an industrial environment, such as guiding machine-assisted movement, or in CAD design, architectural, medical graphics, virtual reality, and other applications.