Source: Tome and Blood
Choose a spell-like ability you possess or a spell you can cast. You gain the benefits of this magic whenever it is used near you.
Prerequisite: Spellcraft 24 ranks, caster level 12th
Benefit: You are attuned to the magic you chose. If another spellcaster within 300 feet of you uses this magic, you also immediately gain the magic's effect as if it had been used on you by the same caster.
You must have direct line of effect to the spellcaster in order to gain the benefit of the attuned magic (though you do not have to know the spellcaster is present, and you can be flat-footed). The magic's duration, effect, and other specifics are determined by its original caster's level.
Special: You can gain this feat multiple times. Its effects do not stack. Each time you take the feat, it applies to a different spell or spell-like ability