1. An eye tracking calibration system comprising: a scene analysis module to receive a video stream from a scene facing camera and to analyze said video stream to detect moving objects and to estimate angular locations of said moving objects over a period of time; a gaze estimation module to receive images from an eye tracking camera and to estimate gaze angles of a user's eye, based on said images, over said period of time; an object trajectory matching module to compute, for each of said moving objects, a first distance measure between said object angular locations and said gaze angles, and further to decide on acceptance of said each moving object for use in calibration based on a comparison of said first distance measure to a distance measure threshold; and a calibration module to estimate an eye tracking calibration angle based on a minimization of a second distance measure, said second distance measure computed between said angular locations of said accepted moving objects and said gaze angles.