Electro-muscular constrictor

From Tardis Wiki, the free Doctor Who reference

The electro-muscular constrictor was an item of the Tremas Master. It had to be worn around the wrist of a humanoid target, thus giving to him complete control over the hand of the victim, remote-controlled through a box.

He used it on Logopolis, on Nyssa, trying to force her to strangle Adric. (TV: Logopolis [+]Loading...["Logopolis (TV story)"])