An attachable apparatus for tracking posture or movement includes a housing having an accommodation space; a sensor in the accommodating space to sense a moving object's posture or movement; a sensing circuitry in the accommodating space to process sensing signals; and a fastening member for detaching the housing from the moving object. Wherein the fastening member includes an object insertion groove that guides the sensor to be matched with the moving object according to a predetermined direction, a fastening member comprised of elastic material allowing detachment from variety of different size moving objects, and a housing coupling member to combine moveable object with the housing.