You clearly have never been to Africa. People do send money with their cell phones to the guy two huts over using mpesa. You can go into almost any shop and trade cash to top off your phone or withdraw cash, even for very small amounts of money. Any shopkeeper with cash and a cell phone can provide this service and they do.

The bitcoin model would work wonderfully there. The fact that you can buy USD with bitcoins will allow a consistent basis of exchange rate and a source of trust. This could really take off considering the fees for mpesa are not cheap.