Travel dial
From Tardis Wiki, the free Doctor Who reference
A travel dial was a wrist-worn teleportation device used for travel on the planet Marinus. Arbitan gave one each to the Doctor, Ian, Barbara and Susan in order to make it easier for them to find the keys to the Conscience of Marinus.
The wearer merely had to twist the dial in order to effect instantaneous travel to the pre-programmed destination. The dials had some commonality with a Time Agency wrist strap, except that they only transported the wearer through space, not time. It was unclear whether the dials would have worked on other planets, or if they were connected to a power source exclusive to Marinus.
