By far the most common claim made for the Million Dollar Challenge offered by the James Randi Educational Foundation (JREF) is dowsing.
Dowsing is as strictly defined the claimed ability to discover underground sources of water or metals by means of a "dowsing rod." Another term used is "divining." However, this terminology and its scope have been expanded and is now used with a far greater range of meanings. Dowsing now includes the claimed ability to discover almost anything, from water and minerals to missing children and archaeological sites. Each dowser will have his or her specialty. The device any dowser will use ranges from the traditional forked stick to just the bare hand. Pendulums, bent wires, wands of various sorts, and swiveled rods and housings are commonly encountered. In every case, the device used is a system in a state of unstable equilibrium, something that cannot easily be kept in a steady condition, and which is subject to very slight tremors, twitches, or changes of inclination. We've seen an astonishing variety of metal springs, coils, wires, balls, threads and bobbing elastic devices, all trembling and vibrating freely, used as dowsing machinery.
Currently, several scientific versions of dowsing rods which purportedly contain actual electronic circuitry, are being sold to government agencies in the USA for very high prices, as much as $14,000. One such stick, known as the DKL LifeGuard, is endorsed and validated by scientists who certainly should know better.