Telepathy pendant
The psychic equivalent of an eavesdropping device, the telepathy pendant allowed the wearer to listen to the thoughts of others. An Arcateenian named "Mary" gave Toshiko Sato, the pendant as a gift. Passing herself off as a human at the time, Mary seemed to indicate that she had obtained the pendant on the alien artefact grey market, though it may equally have come from Mary's home planet.
When worn around the neck, the pendant let Toshiko eavesdrop on the thoughts of people around her. This worked poorly because of the overwhelming number and volume of thoughts that Toshiko exposed herself to in this way, as well as confusing her as to whether her thoughts originated in her own mind or those of other humans. Mary shielded her thoughts. When in Jack Harkness's proximity, she could not read his at all. Jack could project thoughts to her, if he chose, but she could not read his personal thoughts.
The pendant allowed a person to hear both conscious thought and subconscious thoughts of an individual. Toshiko heard Gwen's and Owen's conscious thoughts about their secret affair. When she read Ianto's mind, she not only picked up his pain over Lisa's death but also a darker side of his personality. This is inferred from a raspy voice that could be heared whispering in sync with Ianto's pained thoughts.
Talking it over with Jack and unsure what to do, Toshiko decided that the pendant's abilities were powerful enough to change the world. She crushed it underfoot, destroying it, after talking matters over with Jack. (TV: Greeks Bearing Gifts)
