Requires OBSE
This was a mod request to help with overpowered Essential companions. Now you can set all those Essential companions to non-essential, and not have to worry about your favorite companion dieing permanently. There is a cost to resurrecting (a health penalty) and only one companion can be resurrected every five minutes.
From the readme:
Companion ResurrectCompanionResurrect.espThis mod requires the latest version of OBSE (currently 17b)You can download OBSE here http://obse.silverlock.org/download/Description:Resurrect your companions after a battle by casting a resurrect spell on them.Details:When first running this mod it will add a spell "Resurrect Spell" to the players spell list. Cast the spell on a dead NPC to resurrect them for a cost of 1/2 your current health. Target NPC is resurrected with 1/2 health also. Over the next 5 minutes you and the target NPC gain back 10% of your lost health every minute. While the spell is in effect it will recharge and can not be used again until the 5 minutes is up. This spell can not be used while the player is in combat. The player's health is modified using a Drain Health spell, which can be viewed in the active effects spell list. There will also be an active effect icon in the upper right corner of the screen that indicates the time left until the next health adjustment.Install:Put the CompanionResurrect.esp in the Oblivion Data folder typically located at C:\Program Files\Bethesda Softworks\Oblivion\Data. Start the Oblivion launcher, select data files, and put a check next to the CompanionResurrect.esp. Start the game from there and open the spells tab to equip the "Resurrect Spell" spell.
http://www.tesnexus.com/downloads/file.php?id=29292