Devices identical to those secretly planted in New York City phone booths have been installed in public spaces in Los Angeles and Chicago, BuzzFeed News has learned.

The Bluetooth devices known as "beacons" were installed in bus benches in Los Angeles and train stations in Chicago. Additional information obtained suggests that the devices were also installed in San Francisco, though BuzzFeed News was unable to independently confirm that allegation.

The beacons are manufactured by Gimbal Inc., the San Diego company that made the 500 beacons that were removed from New York City phone booths earlier this month, after a BuzzFeed News investigation revealed their existence.

Taken together, the programs reveal a broad initiative by Gimbal to quietly partner with outdoor advertising companies in major American cities. And they clarify the extent to which technology companies, cities, and brands have begun experimenting with new forms of commercial persuasion, with scant public notice.

Gimbal did not return a request for comment about the programs.

Beacons emit simple, self-identifying signals. Although beacons do not collect any information themselves, they play a central role in Gimbal's phone-tracking technology. Gimbal requires smartphone apps that use its software to get users' "opt-in" permission before collecting data and sending beacon-triggered notifications. When a Gimbal-enabled, customer-approved app "sees" a Gimbal beacon, the phone sends information about the encounter — including the phone's "unique identifier", its location, and the time of day — to Gimbal's servers.

Gimbal's apparent strategy — getting hundreds of its beacons placed in high-trafficked public spaces — contrasts markedly with the indoor, retail-focused applications that have dominated beacon-based marketing so far, such as telling a customer in aisle 12 that polo shirts are on sale.

While municipalities have trumpeted the potential civic uses of a beacon network (to help city agencies send alerts and other messages to smartphones, for example), their implementation has far-ranging commercial implications. And while the outdoor ad firms have so far played down those implications publicly, they've already pitched brands on the consumer potential of beacons.

In its communications with city officials and with BuzzFeed News, Titan Outdoor Advertising initially said that the beacons it installed in NYC phone booths were only being used for testing and maintenance purposes. In several instances, however, the Gimbal beacons installed in Titan's phone booths were used for explicitly commercial purposes.

The Tribeca Film Festival app used the phone booth beacons earlier this year to send festivalgoers notifications about nearby happenings. ShopAdvisor, a mobile shopping app, touted a "pilot program" collaboration with Qualcomm in Manhattan in a solicitation to brands: "There are 500 beacons outdoor beacons placed in Manhattan across all key shopping districts. The ShopAdvisor platform is integrated to work with these beacons." And a promotional image now deleted from Gimbal's website includes what appears to be heat map of beacon-phone interactions in a wide swath of Manhattan: