Self-Pumping Airflow-Inducing Backpack

Today I was walking with a backpack.  I didn't zip the main zipper all the way, and the backpack was only half full.  As a result, with every step I took, the contents of the backpack shifted and air was pushed out of the small opening in the zipper.  The air hit the back of my arm, and since it was a warm day, it felt quite nice.

This gave me an idea.  The energy in walking (or the movement of the backpack's contents) could be used to create airflow to cool the wearer.

In order to create a consistent motion, water could be stored in a separate section.  The back-and-forth motion will create waves of air pressure.  A system of tubing would pump air to the most commonly sweaty areas of the upper body in order to maximize evaporative cooling.  Additionally, a tube could connect to the water tank to provide easy access to drinking water.