This device consists of several thick yellow cables that snake out from a copper-wrapped battery. Attach the cables to various points on a recently fallen comrade, flip the switch, and the body jerks off the ground and spasms mightily while electricity plays over the thinly insulated cables. The smell of burning hair wafts up. In addition to being fun to watch, this display sometimes revives the individual. Goblin jumper cables can only revive a person that has been dead for fewer than ten minutes.WoWRPG 213
Source
Goblin Jumper Cables are made by Engineers with a skill of 165.
The Cables are not soulbound, so if they fail to resurrect but there is another Engineer with enough skill to use them, they can be passed to that player for another try.
NPCs cannot be resurrected, but you can resurrect pets and other players.
Despite its name you do not need to be a goblin engineer to use these, or to make them. Any engineer can do so.
An improved version, Goblin Jumper Cables XL, have a success rate of 50%. They require Engineering skill of at least 265, and do require Goblin Engineering specialization to make.
A further improved version, Gnomish Army Knife, allegedly has a success rate of 66%. They require Engineering skill of at least 350 and the rank of Grand Master Engineer.
These are useful if you are class that cannot resurrect normally, but are able to escape or avoid a fight. (Rogues, Hunters and Mages(with Invisibility) would be a good example)
Occasionally the jumper cables strike you for 50 nature damage.
Patch changes
Patch 2.4.2 (2008-05-13): Goblin Jumper Cables are no longer a trinket item.
Both types of the engineer made Jumper Cables now share a cooldown. It was never intended to allow a player to use jumper cables XL and jumper cables within the same period of time.
Jumper Cables no longer have a chance to break when they fail