Mechanically it might be in the higher ends of the Tome feats, but the only thing that has me really worried is the knocking people prone and staggering - one is conditional(only on a charge), and the other has various workarounds and is already available from other sources (Improved Trip).
Also, should I emphasize further that the direction of the throw is the direction the user of the feat attacked from? 'Back' might not be enough.
Tornado Kick[Combat][Style]
You flip out and kick people through walls.
- +0: Tornado Punch: When attacking as a standard action using an unarmed strike or slam attack, you may declare your attack to be a Tornado Punch. If you hit, your enemy must make a Fortitude Save (DC 10 + 1/2 hit dice + strength modifier) or be knocked prone and thrown back 5' per 5 points of damage your attack dealt (10' per 5 if you have The Edge). In addition, on a charge your unarmed attacks or slam attacks do a base damage of 1d12, unless your base damage is already higher.
+1: Tornado Kick: On a charge you may declare your charge to be a Tornado Kick. If you hit, your enemy must make a Fortitude Save (DC 10 + 1/2 hit dice + strength modifier) or be knocked prone and thrown back 10' per 5 points of damage that your attack dealt (20' if you have The Edge) and an additional Fortitude Save (DC 10 + 1/2 hit dice + strength modifier) to not be Staggered for 1 round. You may not use the Tornado Kick or Tornado Punch against a foe who was targeted by the Tornado Kick last round. You may only use Tornado Kick with an unarmed strike or a slam attack.
+6: Tornado Fists: Your attacks of opportunity may be Tornado Punches. In addition, you halve all falling damage you take (as part of a charge attack or not), and can make a balance check with a DC equal to half the total distance fallen to negate the rest.
+11: Tornado Line: As a charge action, you may charge a target while ignoring enemies or objects between you and the target. As part of the charge you may attack each enemy or object between you and the target - while you don't have to hit or damage enemies between you and the target, you must hit and destroy any objects (such as walls) between you and the target, or you are stopped, and your charge attack ends. Each attack against enemy or object is a Tornado Punch(with the exception that enemies are thrown 90 degrees to the left or right, your choice, instead of straight backwards like a normal Tornado Punch), and the charge attack against the charge target is a Tornado Kick. If you would normally gain multiple attacks at the end of a charge, while using Tornado Line you only gain a single attack. In addition, while using Tornado Punch or Tornado Kicks against objects your attacks ignore hardness. While performing a Tornado Line charge attack you do not provoke AoO's from any enemies directly between you and your charge target(they are too busy flying through the air from your Tornado Punches). You still take AoO's from people not directly in your way and from readied actions/weapons, though. People thrown
+16: Tornado Storm: Each attack in a full attack or whirlwind attack action may be a tornado kick, even if you had tornado kicked a target in the previous round or during this round (this does allow you to tornado kick an enemy against a wall from point blank range multiple times to inflict MASSIVE DAMAGE - (don't forget that the damage done in this manner also affects the wall and could destroy it!).
Special: If a foe is stopped during movement caused by this feat, they take 2d6+your strength modifier+1d6 for each ten feet of movement that didn't occur due to being stopped. This damage counts as bludgeoning damage.
EDIT EDIT: Fix'd.