Metal detector

In 1984, Tegan Jovanka called for help to a man using a metal detector on the mud banks of the River Thames after escaping from the warehouse, but the man had his back to her and wearing headphones so he couldn't hear her. Tegan was shortly afterwards recaptured by Lytton's "policemen", one of whom callously shot the metal detector man — even though he saw and heard nothing. (TV: Resurrection of the Daleks)

Team TARDIS searched through junk planet Seffilun 27 with modified metal detectors. (TV: The Tsuranga Conundrum)