More than 20 million people use the Foursquare social application to tell their friends, family and followers where they are at a given moment in time. The service's new Local Updates service lets small businesses take advantage of those check-ins to send out information updates, texts or promotional offers that are as visually appealing as possible (ala the examples above that come from a New York retailer and restaurant).
Since your followers have already "opted in" by following your business in the first place, you know that the updates are reaching well targeted audience that also happens to be local.
The updates appear in a Foursquare user's friends tab; but they also show up for people exploring new places of interest.
For small businesses, it's another way to reach customers using their mobile gadgets and possibly near your physical store or restaurant without actually paying for mobile advertising.