A psychic wimple was a device used to change the appearance of one's face. It could be targeted to specific people, and increased or decreased in effectiveness at will.
River Song once used one to disguise her identity from the Eighth Doctor. According to both the Doctor and Helen Sinclair, it gave her an appearance similar to Rita Hayworth. Its effectiveness could be adjusted and targeted to affect specific people. (AUDIO: The Eighth Piece, The Doomsday Chronometer)
River also possessed a similar device called a psychic cloak. She gave this to the Eighth Doctor to help him disguise himself from Padrac. (AUDIO: The Crucible of Souls)