One thing that allows Infone to work in Africa is that mobile banking and cell-to-cell money transfers are much more common than they are in America. Another is that in many cases SMS messages are inexpensive relative to the value of the data they could provide.
Two systems for mobile transfer that we investigated were Zain's Me2U and Safaricom's M-Pesa (both links are for the services' Kenyan versions). Although these systems are designed to transfer money only within their networks, they are very easy to use. M-Pesa has been deployed in fewer countries than Me2U, but M-Pesa has been developed along a banking model rather than just for cash transfers.
One system that aims to provide a similar service on top of the American cell network is Obopay.
At the time of writing, Zain-to-Zain SMS messages cost around $0.04 in Kenya and $0.08 in Malawi.