Needs review
Source: Complete Warrior

Description: You can use your opponent's weight, strength, and momentum against her, deflecting her attack and throwing her to the ground.

Prerequisites: Dodge, DEX 13, Improved Unarmed Strike, Combat Reflexes, Improved Trip

If the opponent you have chosen to use your Dodge feat against attacks you and misses, you can make an immediate trip attack against that opponent. This attempt counts against your allowed attacks of opportunity in the round.