Here's an interesting article on research into mobile phones and business opportunities. Much of this research, it appears is taking place in Africa because the mobile phone use there is so pervasive ("Over the past five years the continent's mobile phone use has increased at an annual rate of 65 percent - twice the global average. In June of 1999, Kenya had 15,000 mobile phone subscribers. By the end of 2004 the country had 3.4 million subscribers, and in the last 18 months this number has grown to over 5.6 million, despite the fact that only 200,000 Kenyan households have electricity") and the mobile phone is <i>the</i> tool for all kinds of communication:

A large part of this boost comes from the innovative use of mobile phone technology by local entrepreneurs. In contrast to their use in the developed world, mobile phones in Africa are used for a wide variety of tasks, from sending money to family members to buying a fish from the market. Kenyan business men, farmers, and laborers are finding new uses for a tool thought of as simply a voice communication device in the West, and are coming up with original methods for solving their own problems. For example, contract laborers can now provide their phone numbers to potential employers and move on, instead of having to wait for hours at a workplace in case a job arises. Access to market information through mobile phones also provides rural communities with invaluable information about centers of business; many African fishermen check the local fish market prices on their phones to determine where to bring the day’s catch. The Kenya Agricultural Commodity Exchange (Kace), now provides crop growers with up-to-date commodity information via text message (sms). This allows farmers to access daily fruit and vegetable prices from a dozen markets, and many have quadrupled their earnings because they have access to information about potential buyers and prices before making the often arduous journey into urban centers to sell their produce. The community payphone, another innovation unique to the developing world, has helped bring mobile phone usage to the poorest areas of Africa.