Gnomish Cloaking Device

Source
The Gnomish Cloaking Device is a trinket that can be crafted by Engineers with a minimum skill level of 200. It is usable only by Engineers with a skill level of at least 200.

The recipe for this item is taught by Schematic: Gnomish Cloaking Device, sold by Ravenholdt engineer at Ravenholdt Manor in the Alterac Mountains. Anyone at neutral (the starting reputation) or greater reputation with Ravenholdt can purchase the recipe from him if it is in stock.

Background
The harnessing of chaos energy has given tinkers a more level playing field when dealing with a world of arcane magic. This technology is new and dangerous, and isn’t seen in many devices, but it shows up in unlikely places.

The gnomish cloaking device doesn’t need to be a cloak, necessarily, but the tinker that created it had a flair for style. To all eyes it is a stylish, gray woolen cloak, but the chaos generator is hidden in a small box that is woven into the cloak at the base of the neck and connected by a thin wire to the brooch that clasps the cloak at the shoulder.

When the wearer pushes a button set into the brooch (often hidden) the chaos generator revs up and the molecules in the air around the wearer begin to vibrate at a rate that causes the user to appear to become invisible.