But if you google for pay by sms, you'll see there are A LOT of services for that.

Also here's an article with some statistics: http://www.pewglobal.org/2014/02/13/emerging-nations-embrace...

In Kenya, for instance, 68% of phone users make/receive payments on their phone. And 76% of them use their phones for social networking. At the same time, 82% of Kenyans have a mobile phone. But only 59% have access to clean water. -> http://water.org/country/kenya/

So that's .82*.76 = 62% of Kenyans with social networking vs. only 59% with clean water.

At the time, 93% of South Africans had access to clean water and mobile penetration was at over 100%.

For the whole of Africa, it was ~46% water to 50% phones.

But, as ever, definitions are important. If you have to spend half a day walking to a well for a bucket of water - that counts as access. Similarly, a family who shares a phone each has "access".

It's also a lot easier to build a mobile phone network than a water network. Stick up a tower, power it with a generator / solar power, and point it to a back-haul link. Hey presto, you've got wide area coverage.

I'm surprised it didn't catch on sooner. It's a genius idea for enabling online payments in places where credit cards, PayPal etc. aren't as commonplace as they could be.