1. User interaction system, comprising: an electrical apparatus; a portable pointing device operable by a user for pointing to a region in space; a camera taking a picture, which camera is physically attached to the pointing device so that in operation it always images the region pointed to without imaging the pointing device; a distributed digital signal processor, the digital signal processor being capable of receiving and processing the picture, and capable of transmitting user interface information derived from the picture to the electrical apparatus; at least one localization beacon that emit electromagnetic radiation for use by the digital signal processor in order to recognize where the pointing device is pointing; wherein the digital signal processor estimates a motion or a motion trajectory of the pointing device; and, wherein said digital signal processor recognizes where the pointing device is pointing without utilizing any electromagnetic radiation emitted from the pointing device itself.