????What do you get for your digital-marketing dollars?

????Figuring how much revenue or brand value companies are generating from their investments in digital media seems to be getting more and more complex. While it's simple to measure click-through rates on the web, impressions on mobile devices, tweets on Twitter, and "likes" on Facebook, the business impact in the real world is notoriously difficult to quantify. So as marketers "spread their spending over a widening set of digital options," says Chuck Richard, vice president of Outsell, a research firm based in Burlingame, Calif., "they need more accountability."

????Accountability becomes even more urgent when you consider the numbers. In 2010, for the first time ever, spending on digital media will surpass print media in the U.S., Outsell forecasts. The $120 billion that companies are expected to shell out this year for digital advertising and marketing efforts, including website development, will edge past the $111.5 billion to be invested in print-based marketing.

????Meanwhile, the U.K. has become the first major economy in which spending on Internet advertising has overtaken television. These are milestones in a movement that shows no sign of abating, as digital continues to claim an ever larger share of the corporate marketing budget.

????Yet sometimes companies do know when their digital investments are delivering results. We've searched the globe to discover innovative campaigns that have worked. These case studies represent only two strategies for breaking through the clutter, but they highlight a big trend -- that it's now possible to engage an online audience in novel ways that deliver measurable returns. Each vignette examines the challenges faced by the marketer, the creative digital strategies they deployed, and finally the impact on business.

Pizza Hut's iPhone app: Building your own location-aware pies

????As of two years ago, Pizza Hut had minimal presence in the digital world beyond a rudimentary website, despite being one of the flagship chains of Yum Brands (YUM), the world's largest fast-food restaurant company. Brian Niccol, the Dallas-based chain's chief marketing officer, decided that he wanted to create something innovative and fun that would encourage young, tech-savvy, time-starved customers to order up pies. Since the success of the iPhone was making headlines at the time, it became a natural choice for reaching this demographic.

????Niccol hired the Dallas-based digital agency imc2 to create an app that would, in effect, put the pizza kitchen in the customers' pocket, letting them pinch, drag, and shake pepperoni, mushrooms, and other topping icons onto a graphical pizza crust. The iPhone would then determine which of the chain's thousands of locations the customer happened to be nearest.

????With the app, "you get to engage in the ordering process which is typically mundane and not all that exciting," Niccol says. Equally important, he adds, is the "confidence factor," that by building a model of their pizza, customers are assured that their order is correct.

????The company advertised the new app online, in print, and on television -- even winning a placement in Apple's own iPhone commercial. Within two weeks, the Pizza Hut app (see a demo) received 100,000 downloads. Within three months iPhone users ordered $1 million worth of pizza. Niccol describes the app as "game-changing." The app now has millions of users across the iPhone, iPad, and Android platforms. Niccol expects half the company's phone orders to come from apps and texting, accounting for about $500 million in revenue.

The best job in the world: Attracting tourists to little-known lands down under

????The Great Barrier Reef off the east coast of Australia has long been a famous magnet for scuba divers from all over the world. But the Tourism Queensland agency felt there was potential to also develop the archipelago of islands near the reef as a prime tourist destination in its own right.

????At the agency, a team led by CEO Anthony Hayes sifted through market research that showed their best target audience were young "self-challengers" with a high level of education, a penchant for technology, and a preference for holiday destinations off the beaten track. They needed to reach out to these go-getters across key international markets -- and to engage their interest, they'd need a really compelling hook.