Detecting

The Mexican military deploys a British-made device that can detect from a distance of 500 meters money, drugs, explosives, or weapons. Shaped roughly like a gun, the user points it in the direction of interest, and the "devil's ouija," as it is called, picks up signals from diamagnetic and paramagnetic fields emitted by contraband materials in the device's range. (I have no idea what either of those are, but I'm guessing they have little in common with the magnets on my fridge.)