An interesting Apple patent application discovered on Thursday describes a sensor and alarm system that can be embedded into footwear, granting users a more empirical method on which to rely when deciding to replace worn-out shoes. From Apple Insider:

First filed with the U.S. Patent and Trademark Office in July 2012, Apple's application for a "Shoe wear-out sensor, body-bar sensing system, unitless activity assessment and associated methods" looks to make "smart shoes" that can alert owners when they need replacing.

As Apple describes it, shoes not only provide comfort and protection, but also stability for feet during physical activities such as sports or training. Over time and continued use, a shoe's support decreases, thereby reducing the effectiveness of its protection. There comes a point when a "critical wear level" is reached where a shoe may not provide enough support and can in some cases actually cause foot damage. Because this level of wear may not be apparent to the user, a sensor and alarm system could be a solution to preventing injury.

 Apple's "smart shoes" notify users when they need replacing