This post documents a surveillance system and the civil-liberties questions it raises. The system was first reported by 404 Media, with sources linked throughout so you can verify every claim. Details are accurate as of publication on June 23, 2026. Surveillance programs and the technology behind them change quickly, so check the linked sources for the current picture.
License plate readers were already a problem. Now a defense contractor wants to bolt device tracking onto the same poles. The plate reader knew your car. The upgrade knows your phone, your watch, your headphones and the people who ride with you. It can do this without ever touching your device.
The system is called ELSAG SignalTrace, sold by Leonardo US Cyber and Security Solutions. Leonardo is a publicly traded Italian defense company with a market value above $17 billion. The story was first reported by 404 Media.
What SignalTrace Does
SignalTrace adds wireless sensors to license plate reader deployments. Where an ALPR captures a plate image, SignalTrace also captures the signals your electronics broadcast as you pass. According to Leonardo’s own product sheet, it correlates four categories of device signal with a plate:
- RFID tags: key cards, asset tags, pet microchips
- Bluetooth devices: phones, watches, fitness trackers, wireless headphones
- Vehicle components: tire-pressure sensors, infotainment systems, vehicle hotspots
- Wi-Fi sources: tablets, smartphones, laptops
Every wireless device broadcasts a unique hardware identifier called a MAC address. SignalTrace grabs those identifiers, notes which ones repeatedly appear with the same vehicle, then links the whole bundle to a plate number and time-stamped location. The company says the system can then recognize a vehicle by its electronic profile even when the plate is missing, obscured or wrong.
Leonardo describes this as non-intrusive because it only captures publicly broadcast signals and does not decrypt the content of your communications. That framing misses the point. The harm is not in reading your messages. It is in building a durable, searchable map of who you are, what you carry and where you go.
Why Aggregation Is the Real Problem
A single Bluetooth ping means almost nothing. A single plate scan means almost nothing. SignalTrace exists to combine them. Once your phone, your car and your location are linked and stored, police can pull a profile of your movements over time without ever obtaining your phone or a warrant for it.
This is the part that should worry everyone. Leonardo’s broader direction is documented. In May 2024 the company announced a patent for an electronic detection system that identifies people of interest through their device signatures. The goal is to identify a person, not just a car.
The selling point to police is that there is almost no adoption friction. SignalTrace is pitched as an add-on to ALPR networks agencies already bought. The surveillance expansion arrives quietly, as a software and sensor upgrade rather than a new program anyone votes on.
The Rights in Question
Fourth Amendment. In Carpenter v. United States (2018), the Supreme Court held that police generally need a warrant to obtain a person’s historical cell-site location records, because that data reveals the privacies of life. SignalTrace builds the same kind of long-term location record from device signals collected in public, with no warrant and no notice. The legal gap it exploits is that policy often treats each input separately. A plate image here, a Bluetooth ping there, a time stamp somewhere else. The system’s entire value comes from linking those inputs into one profile.
No way to opt out. You cannot turn this off without turning off your phone, your car and everything else that broadcasts. Like the plate reader before it, you did not consent and you cannot decline.
Mission creep. This is the same pattern over and over. A tool sold for catching serious criminals becomes a standing system that records everyone, then gets a new data layer added on. Each step is small. The destination is a state that can reconstruct your daily life from the signals you cannot stop emitting.
Where This Leaves Us
We used to point at other countries and call this kind of tracking authoritarian. The infrastructure described here is being marketed to American police departments right now, as a routine upgrade to equipment already on the poles. The cameras stopped being about plates a while ago. The question in front of us is whether agencies can convert the ordinary radio noise of daily life into a permanent map of where you have been and who you were with.
What You Can Do
SignalTrace bolts onto the same license plate readers your town may already have, so the place to act is the same as it is for any ALPR: locally, before a contract is signed or renewed.
Find out what is near you with the community map at DeFlock, and use alpr.watch to catch when surveillance tech lands on a local government agenda. Then write your city council, your county board and your mayor and ask the plain questions: does our agency use this, who can search the data, and is a warrant required. Most of these systems are approved in near-empty meeting rooms, which is exactly why a handful of residents who show up can change the outcome.
Sources
- 404 Media: This company will add phone, AirPod and smartwatch trackers to license plate readers
- Leonardo US: License Plate Recognition
- The Deep Dive: Leonardo’s SignalTrace could let police plate readers track your devices
- Business Wire: Leonardo US patent for electronic signature tracking
- Carpenter v. United States, 585 U.S. ___ (2018)