1. An apparatus that monitors at least one physiological property of an organism, wherein the apparatus is configured to be worn by the organism, wherein the apparatus comprises: at least one energy emitter configured to direct energy at a target region of the organism and at a region adjacent the target region, wherein the target region comprises substantially more blood vessels or blood flow than the adjacent region; at least one detector configured to detect an energy response signal from the target region and an energy response signal from the adjacent region; and at least one processor in communication with the at least one detector, wherein the at least one processor is configured to process the detected signals to produce an extracted energy response signal.