A new police tool links your phone to your car without ever using your name

When three minivans leave the school loop together every weekday at 3:15, the phones and smartwatches inside each one are already talking. They probe for familiar Bluetooth pairings, ping nearby Wi-Fi networks, and broadcast little identifiers called MAC addresses that were designed to make connections easier and now make tracking easier too. Stack those signals against a license plate read from the same intersection, run them through the same neighborhood for a few weeks, and a pattern emerges: the same handful of devices rides with the same plate, day after day. The owner of that plate is, in most states, a name and an address on file at the DMV. That is the chain a new product called SignalTrace is built to walk, and the one its vendor's marketing language is built not to name.

SignalTrace comes from Leonardo, a security company whose broader EOC Plus product line already sits next to automatic license plate readers (ALPRs) at police agencies and toll authorities. The product sheet describes a system that does not identify people, only collects the electronic signatures of devices already broadcasting. The capability is documented in more detail in US Patent 11,941,716 B2, which covers methods for grouping consumer devices that regularly travel together and associating those groups with time-stamped locations.

That last phrase, "does not identify people," is the load-bearing part of the marketing. It is true at the moment of capture. A Bluetooth MAC address is a device identifier, not a name. But the product's job is to make the next step cheap. Once a recurring signature cluster is linked to a single license plate, and that plate is tied to a registered owner, the signature becomes a way back to a person without ever re-identifying a phone. The signature is the handle, not the answer.

What makes this more than a product announcement is where SignalTrace is starting to show up. Reporting from Ars Technica describes the capability as tested and marketed, not yet an established police practice, and notes several devices reportedly installed in Oxon Hill, Maryland. A predecessor product appears on a New York State Office of General Services contract price list, which is how vendors get onto the menu any state or local agency can buy from. Both are thin signals, not adoption curves. They are worth flagging because they mark the difference between a press release and a procurement record.

The legal backdrop is uneven. In [Carpenter v. United States](https://www.law.cornell.edu/supremecourt/text/16-402), 585 U.S. 296 (2018), the Supreme Court held that the government generally needs a warrant to access historical cell-site location information (CSLI) from a carrier. [Coverage of Chatrice v. United States](https://theconversation.com/supreme-court-rules-your-cellphone-location-data-is-protected-by-the-fourth-amendment-286424) applied that reasoning to historical CSLI without a warrant. Carpenter is about carrier records, not signals a camera picks up from a curb, and the doctrinal reach of that distinction is exactly the open question. A device signature captured incidentally by a roadside reader is not a carrier record, but it can produce the same kind of movement history once it is linked to a plate.

The reporting work that has to happen before this becomes a settled capability, rather than a tested one, sits in three places. First, deployment scale: how many SignalTrace units are actually in the field, and at which agencies, beyond the Oxon Hill installation and the New York price-list appearance. Second, warrant practice: whether any agency is seeking warrants to deploy the system, treating it as a search under Carpenter, or treating the signature read as a non-search under the plain-view doctrine. Third, retention: how long the device clusters are kept, and whether they are shared through the same ALPR data exchanges that have already drawn criticism in other states.

The pattern SignalTrace is built to exploit is not exotic. People carpool. Families share Wi-Fi. A phone rides in a pocket from home to work to school to home. The product's job is to make that pattern legible, and to attach it to a plate that is already legible. Whether courts treat that as the kind of search Carpenter requires a warrant for, or as a free byproduct of being in public, will determine whether the capability is a procurement line item or a constitutional one.