A motion tracking sensor apparatus configured for real-time, three-dimensional angular motion tracking that can determine the absolute orientation, axis of rotation and angular speed of a body rotating about a point, which is fixed relative to the sensor, without contacting the rotating body. The sensor obtains measurements of the three-dimensional magnetic field of a dipole fixed on the body. In one embodiment, a permanent magnet is embedded in the center of the rotating body, and the time-varying magnetic field is measured as the magnet rotates, and then the instantaneous magnet orientation from the field data is determined. The apparatus is particularly suited for use with devices that are based on a sphere rotating in a cradle such as spherical motors or spherical variable transmissions.