Except it's called M-Pesa, and it's been around for years. According to wikipedia there are 17 million accounts in Kenya alone, with adoption spread around the Africa and India.

It's sometimes called "Mobile Money" and it allows users to send and receive payments using a simple feature phone. The downside is that it's run by evil statists. The good news is that it's fast, it scales without approval from a Council of Neckbeards, and it can't be taken down solely by a bored Russian.