We have a system like this in Sweden, it is called Swish and works wonderful. The way you recieve money is my connecting your mobile phone number to the app and connect it to one of your back accounts in your banks web interface. Then to send money to me you enter my phone number and "swish" the money and you will have it on your bank account within seconds.
The UK has this as well, it's called Paym here. Mind, bank transactions through Faster Payments are also almost always instant, so it's just a convenience feature, nothing majorly new. In the US, inter-bank transfers are not instant at all, so these middleman services provide direct benefits.
