John Hart's vortex manipulator

Captain John Hart owned a vortex manipulator. John referred to it as a "wrist strap". (TV: Kiss Kiss, Bang Bang)

While working as a Time Agent, John made numerous trips through time with his manipulator alongside his partner Jack Harkness. (AUDIO: The Death of Captain Jack)

The vortex manipulator sent and received hologram messages. (TV: Kiss Kiss, Bang Bang, Fragments) It muted sound systems (TV: Kiss Kiss, Bang Bang, Exit Wounds) and communicated with (TV: Exit Wounds) and blocked Torchwood's communication systems. John used it to travel through the Cardiff Rift. (TV: Kiss Kiss, Bang Bang)

John used his manipulator to take Jack Harkness to 27 AD. (TV: Exit Wounds)

John lost his manipulator to Jack Harkness while on the RMS Titanic in 1912. He was, however, able to escape the sinking of the ship through use of a back-up jump bracelet which returned him to London in 1887 on the day of Queen Victoria's golden jubilee. He proceeded to marry Victoria as a means to eventually take control of the British Empire, creating an alternate timeline where he reigned as king while confined to one time period. (AUDIO: The Death of Captain Jack)