1. A security monitoring system, comprising: a local system configurable to be located at a first location and configurable to be electronically linked with a remote system at a second location to provide to the remote system indication of alarm events occurring at the first location, the second location being remote from the first location, the local system comprising: a local database on which are stored templates of data extracted from image data representing images of authorized objects; and an image processing system operable to compare a reduced image template representation of a local object with the stored templates and, if a matching result occurs from the comparison, to suppress indication of an alarm event to the remote system, and, if a non-matching or an inconclusive matching result occurs from the comparison, to transmit indication of an alarm event to the remote system.