Some high level mulling of a very smart person about the future of digital currency, as relates to the involvment of central banks:

Dave Birch in Consult Hyperion’s blog:

So: imagine something like M-PESA but run by the Bank of England. Everyone has an account and you can transfer money from one account to another by a mobile phone app (that uses the secure TEE in modern mobile phones) or by logging in with two factor authentication to any one of a number of service providers that use the Bank of England API to access the accounts or by phoning a voice recognition and authentication service. Drawing on our experiences from M-PESA, TAP and other population-scale mobile-centric system that we have advised on, I think that this API might actually the most important single thing that a Brit-PESA might deliver to the British economy.