Needs review
Source: Player's Handbook

Description: You are skilled at fighting while unarmed.

Prerequisites:

Required for: Air Fist, Blackened Caress, Breaking Blow, Choke Hold, Clever Wrestling, Defensive Throw, Deflect Arrows, Eagle Claw Strike, Earth's Embrace, Exceptional Deflection, Falling Star Strike, Fists of Iron, Flame Fist, Freezing the Lifeblood, Grappling Block, Improved Grapple, Infinite Deflection, Ki Throw, Kiss of the Lotus, Pharaoh's Fist, Rattlesnake Strike, Reflect Arrows, Scorpion's Grasp, Serpent Fang, Shards of Earth (Unarmed), Snatch Arrows, Stunning Fist, Tasaii-do Intermediate, Tasaii-do Novice, Throat Punch, Toothed Blow, Unbalancing Strike, Vile Ki Strike, Water Fist

You are considered to be armed even when unarmed — that is, you do not provoke attacks of opportunity from armed opponents when you attack them while unarmed. However, you still get an attack of opportunity against any opponent who makes an unarmed attack on you. In addition, your unarmed strikes can deal lethal or nonlethal damage, at your option.

Special

A monk automatically gains Improved Unarmed Strike as a bonus feat at 1st level. She need not select it. A fighter may select Improved Unarmed Strike as one of his fighter bonus feats.

Normal

Without this feat, you are considered unarmed when attacking with an unarmed strike, and you can deal only nonlethal damage with such an attack.