Tired of all those single-purpose apps cluttering your smartphone? One to check into your flight, one to rent a car, another to direct you to your eventual destination? Google is working on a solution, a project called “the Physical Web” that would allow users to interact with “smart objects”—such as rental cars, parking meters, or bus stops—without downloading individual apps to use them.

Related to the overhyped “Internet of Things,” the Physical Web would be a network of “smart objects” that each have individual URLs, and broadcast information to nearby users. Bus stops, for example, would broadcast information about the bus schedule to those who search for and connect to it. The project has gotten some recent attention, mostly celebrating its novelty. But the Physical Web raises some serious privacy concerns.

“In principle, Google is designing this so you could roam freely through urban spaces without being identified,” said Walter Valdivia, a fellow at Brookings’ Center for Technology Innovation. But, he explained, companies developing individual smart objects could enable those objects to collect user information. Users interacting with this system could unwittingly provide a “map” of their activities and decisions. “If we become heavy users of the Physical Web, it would be very easy to keep track of your location and what you do,” Valdivia said.

According to Matthew Hindman, an associate professor at George Washington University, this goes beyond the ways in which the government or your ex could already track your movements (through Facebook check-ins, Instagram geotagging, etc.). “We’ve already seen instances where law enforcement is gathering digital data about who was in a particular area at a particular time,” said Hindman, who is currently a fellow at Harvard’s Joan Shorenstein Center for Media, Politics, and Public Policy. “This would have the potential to enhance the scope of that kind of information.”

Valdivia also pointed out that Google has become increasingly targeted in their advertising, and it’s only a matter of time before this project is folded into that effort. “We cannot be naive and assume this is a mere public service.” (Google executives have referred to the Physical Web as “a discovery service.”) Users of the Physical Web could find information from their real-world movements mirrored in their online ads; visit a McDonald’s, for example, and Burger King ads may start appearing on your phone.

The physical proximity of users occupying the same urban space introduces another whole set of privacy red flags. Hindman also used the example of waiting for the bus and “interacting” with the bus stop, by exchanging information: “The concern is that the person standing next to you at the bus stop could also see part of that information,” he explained. “It’s one thing if someone on the internet manages to get your information, but the guy at the bus stop [getting your information] is a totally different kind of threat.”

Both Hindman and Valdivia expressed that it’s still too early to tell how soon the Physical Web could become a reality. Valdivia explained that while much of the physical infrastructure—the “Internet of Things”—is already in place, there are several factors that are difficult to predict. Ultimately, a lot hinges on popularity, third-party investors, and early adopters of the technology. Hindman added that big projects like these often take on an unanticipated “life of their own,” which make setting a timeline for their effects very difficult. “It’s almost guaranteed that the coolest, most exciting things [in tech] aren’t what the creators envisioned in the first place,” he said.

Hindman said that he isn’t a total pessimist about the Physical Web: “The potential implications are exciting—seamless interaction with digital things would be enormously helpful for people.” But, he adds, if that weren’t the case, then privacy discussions would be irrelevant. “If it isn’t useful, and people don’t get acclimated to using it to a point where they can’t live without it, then of course it isn’t dangerous at all.”