Just a first draft here. Wondering about mechanical balance and ease of reading.
Iron Fist Style (combat, style)
Fighting with heavy iron rings on your forearms, your blows strike with the power of a thunderstorm.
Prerequisites: Improved Unarmed Strike, Power Attack, monk level 1st.
Benefit: In place of one of your attacks or as a standard action, you may gain one charge of momentum. You may build momentum in this way a number of times consecutively equal to your monk level. You can hold charges as long as you are engaged in combat. Charges are spent when you make an attack roll.
Roll the damage for a successful unarmed strike once for each charge of momentum gained prior to the attack.
Add +2 to the DC of a stunning fist delivered with one or more charges.
Iron Fist Warding (combat, style)
Your sweeping technique protects you from blows even as you prepare to strike.
Prerequisites: Improved Unarmed Strike, Iron Fist Style, Power Attack, monk level 3rd.
Benefit: As long as you have one or more charges from the iron fist style, you gain a +2 shield bonus to AC. In addition, you only suffer a -2 on attack rolls to fight defensively.
Iron Fist Thunder (combat, style)
You can send opponents flying.
Prerequisites: Improved Unarmed Strike, Iron Fist Style, Iron Fist Warding, Power Attack, monk level 8th.
Benefits: once per round, you may perform an awesome blow combat maneuver when you make a successful unarmed strike with one or more charges from the iron fist style. In addition, you receive a +2 bonus to your CMB to make awesome blow maneuvers.
Iron Fist Master (combat, style)
You can scatter your foes like wind scatters leaves.
Prerequisites: Improved Unarmed Strike, Iron Fist Style, Iron Fist Warding, Iron Fist Thunder, Power Attack, monk level 12th.
Benefits: you may perform an awesome blow combat maneuver whenever you make a successful unarmed strike with one or more charges from the iron fist style. In addition, you receive a +2 bonus to your CMB to make awesome blow maneuvers, and you only spend charges from the iron fist style when you make a successful unarmed strike.
Thoughts?