Stealth Boy (Fallout)

The RobCo Stealth Boy 3001 is a personal stealth device worn on one's wrist.

Gameplay
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 see. Since it works by adding a bonus to the Sneak skill, it only has an effect while sneaking.

Uses
Nightkin NPCs can be seen using Stealth Boys, however, their usage is entirely cosmetic. Unlike the mechanics of traps, one does not have to make a saving throw in order to spot nightkins. However, if the player character uses a Stealth Boy, sneaks and begins a fight in a room with closed doors, enemies from other rooms will not join the fight. A used Stealth Boy cannot be sold. It can be offered in trade, however, the trade will always be refused.

Fallout

 * Giant Footprint special encounter - on the corpse of the stepped on peasant.
 * The Glow Level 5 - in a wall safe.
 * The Cathedral Tower (all floors) - on nightkin sentries.
 * Cathedral lair level 3 - in a locker.

Fallout 2
The device is not present in-game, when speaking to Anna Winslow, they can say that she needs to turn her Stealth Boy off.

Behind the scenes
The device, spelled "StealthBoy," is mentioned in Van Buren.