Scorpion Style

The material below is Open Game Content from a 3PP Source

Scorpion Style (Combat)
You can perform an unarmed strike that greatly hampers your target's movement.
Prerequisite: Improved Unarmed Strike.
Benefit: To use this feat, you must make a single unarmed attack as a standard action. If this unarmed attack hits, you deal damage normally, and the target's base land speed is reduced to 5 feet for a number of rounds equal to your Wisdom modifier unless it makes a Fortitude saving throw (DC 10 + 1/2 your character level + your Wis modifier).