Mobile banking app is becoming popular.
Also, payment via NFC is also increasing in popularity.
Search youtube for NFC for payment for more info also lookup cba kaching app from Australia for example.
In your message suggest how are you going to secure the transmission is it via SSL, TLS other protocols ? do you have a better idea that can create a secure handshake etc..let's have a talk.. Please explain this in your message so we discuss further steps in the app development, cost etc..