From Wikipedia: "A long-range locator is a class of fraudulent devices purported to be a type of metal detector, supposedly able to detect a variety of substances, including gold, drugs and explosives; most are said to operate on a principle of resonance with the material being detected." There is more at the link, but "a class of fraudulent devices" says it all as far as I am concerned. I just wanted to post this so people can find it in the search results in case they are looking.