A question that everyone saying "this is so cool, why don't they do that here" should be asking is why so many people find this option necessary? The core reason is that the banks in Kenya suck. Period. (Okay, I was only there for two weeks but three trips to banks in that time period were more than I would wish on just about anyone...) They make US cable companies and telcos look like paragons of good service and low friction transactions.
In a country where there are not ATMs on every corner, credit card swipers in even the most insignificant bodega, and where you stand in line for an hour to get the cash you will need for a week or month's worth of purchases any system that reduces transaction friction (especially for small-scale purchases) is going to be a win. In places where the economic transaction infrastructure has already pushed down the cost of doing business the appeal of such a system becomes one of convenience rather than necessity.
In a country where there are not ATMs on every corner, credit card swipers in even the most insignificant bodega, and where you stand in line for an hour to get the cash you will need for a week or month's worth of purchases any system that reduces transaction friction (especially for small-scale purchases) is going to be a win. In places where the economic transaction infrastructure has already pushed down the cost of doing business the appeal of such a system becomes one of convenience rather than necessity.