The Transpsychograph-u-lator was a strange device invented by the Twelfth Doctor.
Upon presenting it, Hattie Munroe thought it wasn't real and he had made it up, which technically, he had.
It was supposedly used to track residual psychic traces. Upon using it to search, all the Doctor and Hattie were able to find was seaweed. (COMIC: Beneath the Waves [+]Loading...["Beneath the Waves (comic story)"])