A couple of months back, Google brought check-ins to Latitude, its location-sharing service, through Google Maps 5.1 for Android. Naturally, iPhone users only recently received the same functionality, but some would argue they should be grateful to be included at all. (Kidding. Sort of.) Now, Latitude's inching closer to direct competition with Foursquare and Groupon by offering check-in deals at retailers like RadioShack, American Eagle, Quiznos, and Finish Line. Google is currently namechecking over a dozen nationwide partners, and that list will surely grow as the bandwagon approaches Mach 5. Curious as to how this all works? Check in at RadioShack, for example, and you might receive ten percent off an in-store purchase. Offers are tied to check-in frequency, building on Latitude's three-tiered status system; higher status means better deals. If you'd rather peek nearby offers before you decide to leave the house, head to Google's official check in page in the source link below.