Blindsight, 5-foot Radius( Sword and Fist: A Guidebook to Monks and Fighters, p. 5)
You sense opponents in the darkness.
Blind-Fight (PH) , Base attack bonus +4, Wisdom 19+,
Using senses such as acute hearing and sensitivity to vibrations, you detect the location of opponents who are no more than 5 feet away from you. Invisibility and darkness are irrelevant, though you cannot discern noncorporeal beings. Except for the decreased range, this feat is identical with the exceptional ability blindsight defined in the Monster Manual.