Bio-damper

A bio-damper was a device which could be as small as a ring, that masked the bio-signature of an individual. (TV: The Runaway Bride)

History
The Tenth Doctor gave Donna a bio-damper so that she would be hidden from the Racnoss. However, bio-dampers were ineffective against Huon particles. (TV: The Runaway Bride)

Martin Trueman had a bio-damper to hide the fact that he had the Ancient Lights in him. (TV: Secrets of the Stars)

In 2010, Gavin wore a bio-damper ring he inherited from his father which hid his alien origins. (TV: The Empty Planet)

A bracelet worn by Ruby White incorporated a bio-damper in order to disguise her Qetesh biology. (TV: Goodbye, Sarah Jane Smith)