It's called Dowsing

Dowsing is a type of divination employed in attempts to locate ground water, buried metals or ores, gemstones, oil, claimed radiations (radiesthesia), gravesites, malign "earth vibrations" and many other objects and materials without the use of a scientific apparatus.

Reminds me of this.

The chances of anything coming from Mars are a million to one...

Here's a link to Nana (The Dreaming) if anyone's interested in that part.