First came tracking devices like Tiles and AirTags, marketed as clever, button-sized Bluetooth-enabled gizmos that can find your lost backpack. Then, after bad actors started using the devices to stalk or follow people, came scanning apps to help victims find out whether those same gizmos were tracking them.

Such is the twisted, dangerous path of tracking devices in the wrong hands. That device makers are rolling out scanning apps that can potentially help stalking victims is a win for privacy—but with a couple of big asterisks. Tile’s new scanning app shows why.

The company, which has sold over 40 million trackers, is the latest manufacturer to roll out a scanning app. Its Scan & Secure feature allows people to determine if someone is tracking them using a Tile product. This follows Apple’s introduction in December of an Android app called Tracker Detect that allows people using Android devices to find out if someone is tracking them with its popular AirTag device or other devices equipped with sensors compatible with the Apple Find My network.

As we noted when Apple released the Android app, AirTags are an order of magnitude more dangerous than other device trackers because Apple has made every iPhone that doesn’t specifically opt out into part of the Bluetooth tracking network that AirTags use to communicate, meaning AirTags’ reach is much greater than other trackers. Nearly all of us cross paths with Bluetooth-enabled iPhones multiple times a day, even if we don’t know it.

To use the Tile scanner, you need to download the Tile app on your phone and tap Scan & Secure under settings. Users need to walk around or move/drive away from where they launched the app, which will scan six times to detect Tiles and Tile-enabled devices that may be traveling with them. The app displays the scan results showing both the known and unknown Tiles and Tile-enabled devices it detected and how many times they showed up in the six scans.

The need to download an app and pro-actively run a scan to find out whether someone is tracking you is the major weakness of this mitigation. Victims of stalking or partner violence may be completely unaware that a device is tracking them, much less which kind of device is being used. For the scanning apps to be effective, a target of tracking would need to know what device is being used, then find and download a scanning app for that device. A world in which survivors of stalking and abuse need to download a separate app for every type of physical scanner and use it to run dozens of individual scans is better than what we have now, but this is not a solution that scales well.

EFF calls on the makers of physical trackers to agree on and publish an industry standard that would allow developers to incorporate physical tracking detection into both mobile apps and operating systems. We continue to call on these tech giants to work together to address the threats their users face from ubiquitous, cheap, and powerful physical trackers. It’s easy for stalkers to use these devices to harass and threaten their victims. It should be easier for victims to find out if this is happening to them so they can protect themselves.