Your unarmed blows are more powerful.

Prerequisite: Improved Unarmed Strike, Base Attack Bonus +6

Benefit: Deal damage as if you were a monk half your character level (minimum 1). If you have levels in monk or brawler, apply 1-1/2 times your character’s Strength bonus to damage rolls with unarmed strikes.

Special: A monk adds this to his list of bonus feat options at level 6.