Want to see the Vince Lombardi Trophy that goes to the Super Bowl winner? Take a left in 15 feet. Looking to buy some Super Bowl merchandise? Try the fourth floor of Macy’s, straight ahead.

The Super Bowl remains the biggest mass-market advertising event in the country. But this year, a new kind of advertising — personalized and based on physical location down to a matter of feet — will greet fans in Times Square and MetLife Stadium, where this weekend’s championship game will be played.

At both locations, the National Football League has sprinkled tiny wireless transmitters that can send finely tuned messages to smartphones. It is the boldest test yet for a months-old technology that could change how brands of all sorts market to their customers.

For now, the alerts are mostly limited to practical news (like the nearest entry gate) or promoting in-store sales (say, for your favorite chocolate) in the first wave of establishments using it. But already the technology has privacy advocates and legal experts brimming with concern about the implications. Smartphone users could potentially be spammed with advertisements, they say, and a company that collects the data might be inclined to sell it.