Admonitor

Admonitors is the name of a magical instrument resembling thick metal cuffs that monitors the magical activity of the wearer. The British Ministry of Magic employs these against suspects under surveillance.

History
Torquil Travers placed a set of admonitors on Albus Dumbledore in 1927 in response to the latter's apparent unwillingness to fight Gellert Grindelwald for the Ministry.

Behind the scenes

 * Since the cuffs allowed Travers to keep track of any spell Dumbledore used while he wore them, it is possible that a spell had been placed on them similar to the Trace.

Appearances
Fantastic Beasts: The Crimes of Grindelwald - The Original Screenplay

Fantastic Beasts: The Crimes of Grindelwald