The Pentagon is testing technology that will let a smartphone identify you by the way you walk, as well as how you hold the device and swipe across the screen.

Gait serious: The idea is to use traits such as a person’s walking motion, or gait, as  biometric signals, adding an additional layer of security. We already have passcodes and face recognition, of course, but this technology would let a device know as soon as someone else walked off with it. Gait detection has long been known to be a good biometric, but now the technology is around to make it practical.

Mobile mayhem: Mobile gadgets are a weak link in cybersecurity that hackers can exploit to breach bigger, more valuable systems. The issue is especially serious for big corporations, but is also relevant to national security.

Beyond spooks: The Pentagon says it is working with smartphone manufacturers to make the technology widely available. It relies on the sensors already found inside smartphones, using software to score a probability—based on movement—that the device is being carried by the right person.

Privacy problems: Biometrics can also raise privacy issues, since they offer a new way to keep tabs on you. Face recognition has emerged as both a useful security tool and a powerful way for companies and governments to track people. In China, people’s gaits already offer a new way for Big Brother to watch over them.