Have you heard of Proximity Marketing? You have? Great.
Proximity marketing is the localized wireless distribution of advertising content associated with a particular place. Transmissions can be received by individuals in that location who wish to receive them and have the necessary equipment to do so.
Distribution may be via a traditional localized broadcast, or more commonly is specifically targeted to devices known to be in a particular area.
Read more about it on https://en.wikipedia.org/wiki/Proximity_marketing