1. A method for continuously monitoring the gaze direction of a driver of a vehicle over time, said method comprising: receiving video captured by a mobile image-capturing unit comprising camera within a vehicle, said camera of said mobile image-capturing unit mounted facing a driver of said vehicle; extracting frames from said video; detecting a facial region corresponding to a face of said driver within said extracted frames; computing feature descriptors from said facial region, said feature descriptors comprising at least one feature vector comprising a multi-dimension feature vector: normalizing each component of said at least one feature vector Including face part locations and sizes associated with said facial region to render said feature descriptors invariant to facial translations and scaling as well as pixel resolution, wherein said normalizing comprises normalizing a position and size of said face by lengths of axes of a face coordinate system defined by a square surrounding said detected face with an origin located at a top-left corner of said square: and applying a gaze classifier with respect to said vehicle, said driver, and said camera, wherein said gaze classifier receives said feature descriptors as inputs and outputs at least one label corresponding to at least one of a predefined finite number of common driving gaze directions to identify a gaze direction of said driver of said vehicle.