The Federal Trade Commission announced a consent order Thursday with Nomi Technologies, which it said did not abide by its own promises to allow consumers to opt out of being tracked while they shop.

This is the first enforcement action by the FTC against a retail tracking company.

Nomi is one of several companies that have developed ways to use consumers' cellphones to track their real world movements for commercial purposes. According to the FTC complaint, the company used censors in stores to collect the MAC address -- a code unique to each phone -- of a shopper's smartphone when the device searched for WiFi networks, a thing many phones do almost constantly by default. The movements of users both in and outside these stores were tracked by this unique ID along with the device type, when the shopper was observed and the signal strength of the device, which could be used to tell how nearby a shopper was.

Nomi collected information on about 9 million mobile devices during the first nine months of 2013, the FTC alleged. It used a technique called "hashing" to obscure MAC addresses that could be used to identify a particular smartphone. But it still generated a unique code that was associated with those devices allowing them to be tracked over time and potentially revealing sensitive information about a shopper's movements, according to the FTC.

The company used the tracking information to give retailers insight into their customer base -- for instance, how many repeat customers they had during a given period and how long consumers stayed in the store, the FTC said.

These reports did not share information about specific shoppers, but the FTC found Nomi had violated its own privacy policy.

Nomi did not provide a way for consumers to opt out of being tracked through the physical stores they were shopping in, as it promised in late 2012, the complaint alleged -- in fact, consumers were not told they were being tracked at all. It did provide a way to opt out through its Web site, but that was not enough, according to the FTC.

“It’s vital that companies keep their privacy promises to consumers when working with emerging technologies, just as it is in any other context,” said Jessica Rich, director of the FTC’s Bureau of Consumer Protection in a news release. “If you tell a consumer that they will have choices about their privacy, you should make sure all of those choices are actually available to them."

Under the terms of the settlement, Nomi agreed to abide by its privacy promises and not misrepresent consumers' options to block being tracked. The agreement will be open for public comments for 30 days before the commission finalizes it. The commission voted 3-2 to issue the complaint and accept the consent order, with Commissioners Maureen Ohlhausen and Joshua Wright dissenting.

Nomi said in a statement that it was pleased with the agreement. "We continually review our privacy policies to ensure that they follow best practices and had already made the recommended changes in pursuit of that goal by updating our privacy policy over a year and a half ago," the statement said.