The Defibrillator implant is an important piece of equipment in RAGE. It brings the protagonist back to life when he has taken too much damage and is close to death. It can also shock any nearby enemies leaving him to wake up in a safe environment. [1]
The player can get an upgrade by doing the quest "Defibrillator Upgrade" which will add another defib chance.
The player can also receive another upgrade from the quest "Finding Feltrite" which speeds up the recharge time of the Defibrillator.