Magical Aura Dowsing (3.5e Spell)

As you cast Magical Aura Dowsing, you must touch a forked stick. For 1 round/level, the stick gains the ability to point itself in the direction of the nearest aura that fits your requirements.

As a free action once per round while holding the stick, any character may specify a spell school and minimum and maximum aura strength. The stick points in the direction of the nearest aura that is of that spell school and has an aura strength within those limitations. If there is no such aura, it doesn't point at anything at all.

Auras behind barriers (such as 1' of stone, 1" of metal, a thin sheet of lead, or 3' of wood or dirt) are ignored.

Note that the stick can detect itself; asking it to find a Faint Divination aura will make the stick break.