ARGUS

The ARGUS device was piece of bomb detection equipment used by the UNSC. It was mainly used against the Insurrectionist terrorist bombers, though they were often fooled by coating the bombs in normal chemicals. The larger ARGUS detectors were deployed at major transportation hubs to limit the movement of bombs, and smaller tactical versions, were employed by Marines during raids. They were micro laser spectrometers designed to 'sniff' out chemicals used in explosives in the air. They were used on the ARGUS Drone.

Historical Reference
"ARGUS" is most likely used as a reference to Argus from Greek mythology. In the myth, Argus was a guardian with one thousand eyes (The ARGUS drones supposedly also had this "all-seeing" ability to detect bombs).