1. A system for use in monitoring one or more conditions of a subject's body, the system comprising a control unit comprising: an input port for receiving input data comprising image data in the form of a sequence of speckle patterns generated by a portion of the subject's body during a certain time period and data indicative of at least one external stimulation applied to said portion of the subject's body during said time period; a memory utility for storing one or more predetermined models, the model comprising data indicative of a relation between one or more measurable parameters and one or more conditions of the subject's body; and a processor utility configured and operable for: processing the image data utilizing the data indicative of a waveform of said at least one external simulation, said processing comprising determining a spatial correlation function between successive speckle patterns in the sequence, and determining a time varying spatial correlation function in the form of a time-varying function of at least one feature of the correlation function, the time-varying spatial correlation function being indicative of a change of the speckle pattern over time; selecting at least one parameter of the time-varying spatial correlation function, and applying to said at least one parameter one or more of the models to determine one or more corresponding body conditions; and generating output data indicative of said one or more corresponding body conditions.