I am adding Overdraft Protection to v1.1.
This means that if you are at the cashier and he/she says you owe the store 50 bitEUR for the groceries but you only have 45 bitEUR, then the app settings screen will allow you to set BTS or other assets as a backup funding source for your bill, up to a certain amount. I hope to use the Blocktrades api for this as well.
So far, this is looking like a possibility. I want the user experience to be as simple and friendly as possible.