When migrant workers send money home to relatives in Africa, they typically pay 12.3 percent to money transmitters. It’s a big business. Overseas Development Institute estimates the total annual fees paid to money transmitters to be $1.4 billion. These businesses have now found a competitor in bitcoin. A new service, BitPesa, allows bitcoins to be transferred to Kenya and Ghana for a 3 percent flat fee. Bitcoins can then be converted into local currency. Using a cell phone for payments is common in some parts of Africa; in Kenya, 70 percent of all national payments are made through M-Pesa, a mobile money service.