Stattenheim remote control
A Stattenheim remote control is a device used by Time Lords to control their TARDISes after linking them to it.
The Rani's remote looked like a black remote with one button (TV: The Mark of the Rani) while the Second Doctor's one looked like a small rod with a recall disc one side and gold prongs on the opposite one to put it inside the teleport control dome of his TARDIS console. (TV: The Two Doctors)
The Master created one to retrieve his TARDIS. (PROSE: First Frontier) The act of whistling was not technically required, but was useful to focus the mind to "call" the TARDIS to the user's location. (PROSE: Timewyrm: Exodus)
The Second Doctor's teleport control where he stored the recall disc of the remote gave dual control of his TARDIS to the Time Lords (TV: The Two Doctors) on Gallifrey. (AUDIO: The Black Hole)
When the Sixth Doctor asked the Second Doctor where he had got a Stattenheim remote control, the Second Doctor said that "Some of us have earned these little privileges." (TV: The Two Doctors) According to one account, the Second Doctor had been granted his remote control by the Celestial Intervention Agency. (PROSE: World Game) According to another account this remote was given to him by the Monk who stole it from Pavo, in order to get the Doctor away from himself. When the Doctor attached it to his TARDIS, it synchronised it with those back on Gallifrey, changing its interior appearance. It also created a dual control, allowing Gallifrey to control his TARDIS. Though the Monk reassured him that they'd be unaware of whose TARDIS was linked, merely directing the TARDIS to the input coordinates. (AUDIO: The Black Hole)
Following the defeat of Chessene and the Sontarans' plans to use the Kartz-Reimer module, the Second Doctor held the Stattenheim remote control and whistled. His TARDIS then rematerialised at the Spanish hacienda he was in. (TV: The Two Doctors)
The Master once tried to steal the Second Doctor's remote control. (GAME: Destiny of the Doctors)