1. A monitoring apparatus to monitor a region of interest for activity, the apparatus comprising: a plurality of sensor channels to produce numerical sequences proportional to energy of at least two energy modalities transferred to respective sensors thereof during commission of an activity; and a signature detector to determine whether a known activity is committed by matching dimensionally-reduced representations of the numerical sequences with dimensionally-reduced representations of known numerical sequences containing signal characteristics defined by energy transference in the commission of the known activity, and to provide an indication of the known activity upon positive determination of the match.