Just the product Apple needs to recharge its falling stock—smart shoes. They may not be rolling to market yet, but Apple Insider just uncovered an application Apple filed with the U.S. Patent and Trademark Office in July 2012 that described a “shoe wear-out sensor, body-bar sensing system, unitless activity assessment and associated methods.” In English? Smart shoes that alert the wearer when it’s time to replace them.

The shoes feature sensors that track their wear and usage. Progress in the smart shoes is charted through a companion app which can alert the user when the shoes need replaced, or the alerts can be made via built-in LED lights, speakers or displays. Why is a sensor necessary when you can just look at the shoe, one may ask? As Apple stated in its application, “Shoes provide comfort and protection for feet. When a critical wear level is reached, even if the shoe looks like it is not particularly worn, the shoe may not provide adequate support and may, in fact,cause damage to the feet.”

A standard walking shoe, for example, reaches its “critical wear level” after 500 hours and need to be replaced.

In its patent application, Apple describes embedding the electronics into the shoe’s heel, where there is plenty of room to house components. The sensors can then be placed in the sole, heel and along points that could indicate how worn the show is. The sensors—which could be accelerometers, pressure sensors or piezoelectric flexing sensors—could also include pedometers, activity and motion detectors, as well as a body bar that could detect weight and resistance.

The patent then includes an algorithm through which data is processed. The algorithm could be set according to a shoe manufacturer’s specifications and would determine at what point the shoe reaches the “critical wear level.”

The technology is fascinating if not practical, although its not likely Apple will be competing the likes of Nike and Reebok for space on shoe store shelves any time soon. Piper Jaffray analyst Gene Munster said earlier this month although he believes Apple will eventually introduce a wearable computing product, Bluetooth-enabled smart watches or Google-like glasses would be higher on his forecast.

But if Apple does launch a shoe… imagine the possible celebrity endorsements.

[Image via USPTO]