bstract The present invention relates to the field of electro-mechanical devices that communicate with a computer system for tracking the motion of a human body, animal body, building, machine or the like. The invention presents an innovative, electro-mechanical spherical joint that is able to detect its rotation in three dimensions; it is comprised of a rotating ball 101, a socket 102, a stick 103, a sensing point 104 and a dotted sensor 105. The invention can form a linear, grid, or 3D composition to detect the linear, surface, or mass motion respectively, to serve many fields such as computers, buildings, medical/health care, movie production, sports, education, robotics, and remote controlling among others.