An input device (1) for data processing apparatus (12) comprises a dish (2) having a convex lower surface (3) which rests on a base (10) and can tilt in a plurality of directions with respect to the base, and a concave upper surface (5) in which is positioned a movable member such as a ball (6) which can move with respect to the concave upper surface. A user is supported on the movable member, in a standing, sitting or kneeling position. The dish is provided with a motion detector module (8) which detects movement of the dish in response to forces applied to the dish as a result of actions performed by the user, and which produces signals in response to such movement. An interface (9) serves to output the signals to the data processing apparatus.