A writing stylus (100) having a motion sensor (204) for sensing the movement of at least one end 110 of the stylus relative to an adjacent surface is described. The stylus has an elongated housing (104) and a cap (102). The motion sensor generates signals corresponding to the relative motion of the surface to the sensor. The cap is removeably carried on at least one portion of the housing which also has the motion sensor. The cap comprises a light passage (118) adapted to allow the motion sensor to sense the translation of the surface adjacent to the cap, through the cap. In a first input mode the motion sensor is used for sensing manual hand writing motion. In a second mode, when the cap is carried on the housing and is placed over at least the motion sensor, the motion sensor senses the motion of a surface adjacent to the cap such as a users finger. In this mode, the stylus functions a multiple axis input device such as a thumbwheel.