Stealth Boy

RobCo Stealth Boy 3001 is a personal stealth device worn on one's wrist. It generates a modulating field that transmits the reflected light from one side of an object to the other, making a person much harder to notice (but not completely invisible). It was used by the Nightkin elite super mutant units of the Master's army. It weighs 3 pounds.

History
Stealth Boy is an unstable technology reverse engineered by the U.S. from the Hei Gui stealth armor, worn by elite Chinese "Black Ghost" counterinsurgency/terror units.

Side effects
Some time after they acquired the Stealth Boy technology, the Brotherhood of Steel experimented with those devices. It turned out that prolonged use causes the user to suffer paranoia, delusions, and eventual schizophrenia. When this was discovered, the devices were banned and the team disbanded. However, it was not known that the team had already begun to suffer the effects of the device. Thinking the disbanding of their team to be a conspiracy, they decided to steal the Stealth Boys and form a new covert operation called the Circle of Steel.

Appearances in games
Stealth Boy can be found in the first Fallout and Fallout 3, although it is mentioned in Fallout 2 and its description is present in Fallout Tactics files. The device's backstory wasn't developed until Van Buren, the cancelled Fallout 3 by Black Isle, where it was spelt as StealthBoy to prevent it from being confused with the "Stealth Boy" playing style.