Invest Armor

 
Prerequisite(s): Light, Medium, or Heavy Armor Proficiency (Depending on armor type)
 
Benefit: You can expend your psionic focus to infuse your armor with psionic energy. This gives you an increase to your AC of 3, until the next time you are hit. Using this feat is an immediate action and can be taken during another creatures turn, in reaction to being affected by an attack. You must decide to use this feat before the result of the attack against you is announced.
 
Source: Races of Stone