What is "sniffers"

Usage examples of "sniffers".

And if, on their return, the regents should set their Deryni sniffers to questioning Javan, along with everyone else left at Valoret Castle tonight.

Pajunggs were dickering with several Companies for satellites and emission sniffers, hoping to cut into the hordes of smugglers hitting the surface of Avosing, drawn like flies by the sweetamber and the drugs distilled by the foresters from local plants, but they wanted the Avosingers to pay for the scanners.