$7 Smartphone Add-On Detects Hidden Cameras in 5 Seconds

Finding a hidden camera in your Airbnb just got a whole lot easier.

Researchers at the Korea Advanced Institute of Science and Technology partnered with two Singapore universities to create SweepLED, a $7 smartphone attachment that detects hidden cameras in about five seconds. The device tackles a growing privacy concern that's become so serious, Airbnb banned all indoor security cameras in rentals two years ago.

The problem with existing camera detectors is simple. They shine a light and look for reflections, but everything in a room reflects light: mirrors, lamps, glasses, even your toaster. Users end up with dozens of false alarms and no real answers.

SweepLED solves this by watching how reflections change over time. The device fits onto the back of your phone like a case and contains 15 small LEDs. When you point your phone at something suspicious and hold still for a few seconds, those LEDs rapidly sweep light across the object from different angles while your camera records.

Camera lenses have a unique optical structure that creates distinct reflection patterns as light moves across them. A mirror or shiny plastic reflects light differently than a hidden camera lens does. The software uses AI trained to spot these specific patterns rather than just flagging anything shiny.

The process happens in stages. First, the system stabilizes your video because your hand might shake slightly. Then it compares frames captured with LEDs on versus off to isolate the exact reflections created by the light sweep. Finally, the AI analyzes how those reflections changed over time.

The researchers tested their prototype on 30 different objects, from actual hidden cameras to regular household items. The system achieved 94% detection accuracy across all tests.

The Ripple Effect

Privacy violations in rental properties have left countless people feeling unsafe in spaces where they should feel secure. This technology puts power back in travelers' hands without requiring expensive equipment or technical expertise. For less than the cost of a meal, anyone can scan their hotel room or vacation rental with the phone already in their pocket.

The prototype uses about $7 worth of components, making it affordable enough for widespread adoption. The researchers presented their findings at ACM MobiSys 2026, bringing the device one step closer to commercial production.

Protection and peace of mind might soon be as simple as a phone case.