Even more to the point - Kenya and Tanzania have had M-Pesa (which allows payments and transfers via mobile phones) since 2007 (http://en.wikipedia.org/wiki/M-Pesa). Note that this is not necessaries smart phone stuff - just a plain 'ol mobile phone with text capabilities will do.

Also, I was visiting that region in 2006 and was struggling to add some phone credits to my phone that I had just purchased. Some random guy in the queue offered to send me credits from his phone, and I was pretty much blown away with how easy it was.