A security device and system is disclosed. This security device is particularly useful in a security system where there are many security cameras to be monitored. This device automatically highlights to a user a camera feed in which an incident is occurring. This assists a user in identifying incidents and to make an appropriate decision regarding whether or not to intervene. This highlighting is performed by a trigger signal generated in accordance with a comparison between a sequence of representations of sensory data and other corresponding sequences of representations of sensory data.