You have a greater chance to resist attacks against your agility, but at a cost.
Prerequisite: Lightning Reflexes.
Benefit: Before rolling a Reflex save, you can decide to activate this feat, which gives you a +6 bonus on your saving throw. After the saving throw is resolved, regardless of the result, you are prone and dazed.
Source: Savage Species, page 31. Removed the last sentence and hyperlinked the prone and dazed conditions.