Why Location Marketing Is New Point-of-Purchase
Forget Foursquare or Gowalla: Soon every website and service will be able to tell where you are, opening up the floodgates for location-based marketing and blurring the budget lines for advertisers.
yes you can rely on a high price purpose built app to tell you when your users are in your store....however - dont forget QR codes located "within the store" from which a customer can snap an image "land on a mobile page" (changed daily so they cant just save the landing page) and receive something of value in return for their participation is the perfect way to combine mobile and location. Still dont know what a qr codes is? check out http://www.Cognation.net/QR for a 60 second overview.