How would they even know which restaurant to call? This only works in the online advertising world because whenever John enters a shop, restaurant or other est

How would they even know which restaurant to call? This only works in the online advertising world because whenever John enters a shop, restaurant or other establishment his photo is taken and sent to a central authority. That central authority can then sell space in some of those shops to push a product or service to him based on the history of shops he's entered.