Time magazine, for example, has formed a partnership with Foursquare, a location-based mobile check-in service, for the conventions, in which Time has provided content that users can unlock when they get to certain locations in Tampa and Charlotte.
Unlike some Web-based phenoms, the location check-in service Foursquare has an obvious potential business model: local ads based on your geographic location, perhaps coupled with inferred interests from your previous check-ins.