Eagle comes from an academic background--he has appointments at Harvard and MIT and once more than a year as a Fulbright professor in Kenya--and his roots lie in using technology for development and social good. Jana was born, in part, of Eagle's success in setting up a network in rural villages in Kenya for nurses to text in status reports on supplies of hospital blood banks.

Jana's network, which is connected directly to the computer systems used by mobile carriers around the world, doesn't send actual money; instead, it gives mobile-phone credit. In emerging markets, where, according to Eagle, the average user spends 8%-12% of his or her income on prepaid mobile service, that's almost as good as cash.

From his office in Boston, Eagle can credit money into the prepaid accounts of more than 2 billion handsets around the world, instantly. "We know the 850 million prepaid phone numbers in India," says Eagle. "We can pick one at random, tap in '50 rupees,' and when I push enter, no matter where it is in India, whether it's an old school Nokia or an iPhone, that rural subscriber is going to say "Hey I just got 50 rupees."

Jana mainly reaches users through a mobile-friendly website or--for the minority of its users with full browsers on their phone--a Facebook app. Users can choose from a list of tasks they can perform in exchange for credits: For example, Microsoft once asked Jana to have its users answer questions about an interface Microsoft was testing.

Often, Jana links its promotions to purchases in the physical world. "In the Philippines, if you go out and buy a particular brand of candy bar, if you get three of your friends to also buy it, all of you get it for 50% off." says Eagle. "We can validate the purchase because 7-Eleven is now printing Jana IDs on every receipt they have. At any of 713 7-Elevens, it's on the receipt." In another promotion, consumers in Indonesia who purchased two or more Danone yogurt products got 5,000 rupiahs ($0.52) worth of airtime directly on their phones.

Marketing to the Millions

Of course, Jana is not the only firm enticing mobile-phone subscribers to answer marketing surveys and redeem coupons; it merely has the biggest reach. But reach is not the only thing that matters, says Donald Fitzmaurice of Brandtone, one of the few companies with ambitions as broad as those of Jana. Advertising is an extremely local phenomenon, tuned to regional tastes and trends, he notes. "If you were to compare us with Jana," says Fitzmaurice, "Jana claims access to everyone in the world. What we do is we combine total access with the ability to work closely with brands to provide the platform that customers actually need in that market."

Compared with Jana's, Brandtone's technological approach seems relatively low-tech. Instead of a mobile website, it mostly reaches its customers via text messages and voice call. This is necessary, says Fitzmaurice, because the average user in emerging markets is on a "three year old gray-market Nokia that only does voice and text." But Brandtone combines this technique for reaching mobile subscribers--which will be in the "top 11 developing and emerging markets in the world by 2013," says Fitzmaurice--with teams of marketers in every country in which the company operates.

So in South Africa, for example, Brandtone set up a promotion that offered mobile-phone credit to anyone who bought a particular brand of washing powder. A code was printed inside each bag of powder, and buyers who texted the code to a certain number were called back with a recorded message from Nkanyiso Bhengu, a popular South African radio celebrity, followed by a three-question marketing survey. The promotion ran in six languages and reached millions of people.