Smart glasses aren’t just the stuff of Hollywood anymore: You can buy a pair right now. Devices like Ray-Ban Metas come equipped with speakers, a microphone, embedded cameras, and connectivity to your smartphone—all in a package that largely looks like a normal pair of glasses. That’s great for enthusiasts who want a hands-free smartphone experience when out and about, but not so great for anyone who dislikes the idea of invisible cameras everywhere.

There are two sides to these privacy worries. One is the personal angle. Many of us don’t want the people around us shoving their smartphone cameras in our faces when we’re out in public, but at least then we’d know we’re being recorded. These embedded cameras are tough to spot unless you know what you’re looking for, which means there’s a feeling of always being watched by anyone walking past wearing glasses. On the other hand, there’s the larger privacy concern that comes with the territory of a huge company like Meta. Just last week, we learned the company plans to bring facial recognition tech to its Ray-Ban and Oakley smart glasses with a feature called “Name Tag,” which would give the wearer insights into the people they encounter using Meta AI. Taken together, smart glasses pose an unprecedented privacy and security risk for those of us living our lives, when both our neighbors and law enforcement have the accessibility to spy on us without our knowledge.

Of course, what can you do? If these glasses are legal, and they’re relatively inconspicuous, how can you protect yourself from the average Ray-Ban Meta-wearing Joe? By the time you get close enough to tell whether or not they’re wearing smart glasses, you’re already in view of the camera.

“Nearby Glasses” tells you when someone is wearing smart glasses in your area

Enter “Nearby Glasses,” a new app that spills the beans on smart glasses wearers near your location. As reported by 404 Media, the app is made by developer Yves Jeanrenaud, and scans for smart glasses’ “distinctive Bluetooth signatures” (also known as “advertising frames”) to identify them in your immediate area. Jeanrenaud was able to use a directory of Bluetooth Low Energy (BLE) manufacturers to build a list of smart glasses the app can scan for, including devices from Meta, Luxottica Group S.p.A, and Snap. If the app spots one, it sends you a push notification.

The app can’t currently distinguish between smart glasses and mixed reality headsets, however. As such, you may get an alert saying there are smart glasses nearby, but because the app picked up the Bluetooth signals from a Meta Quest headset. That said, these are much easier to spot than smart glasses, and are far less likely to be worn inconspicuously in public spaces.

Nearby Glasses is available for Android today, on both the Play Store as well as Github. Jeanrenaud says an iOS port “is in the making.”