We describe a system that detects independently moving objects from a mobile platform in real time using a calibrated stereo camera. Interest points are first detected and tracked through the images. These tracks are used to obtain the motion of the platform by using an efficient three-point algorithm in a RANSAC framework for outlier detection. We use a formulation based on disparity space for our inlier computation. In the disparity space, two disparity images of a rigid object are related by a homography that depends on the object's euclidean rigid motion. We use the homography obtained from the camera motion to detect the independently moving objects from the disparity maps obtained by an efficient stereo algorithm. Our system is able to reliably detect the independently moving objects at 16 Hz for a 320 x 240 stereo image sequence using a standard laptop computer.