One week-plus into owning an iPhone 3GS—and more than a year into reading, writing and editing iPhone app stories—I couldn’t think of an app announcement that would grab my attention, but Barnes & Noble has done it. The free B&N Bookstore iPhone app isn’t the flashiest but flash it at a B&N Cafe barista in one of its stores and you can get a free tall cup of Starbucks coffee. It’s not a bottomless cup—each app download comes with a one-time coupon code—but it is a good gimmick to claim a few minutes of attention in a very crowded field. What will really make it work: if B&N starts delivering all its coupons this way, in addition to the e-mail that I never remember to print out.