Ok. I think your main problem right now is that you are falling in the 'anti money laundering' category from the point of view of the bank.

As for liability, for an Iphone application I think that since the transaction is between the customer and Apple that you are more or less out of the windy zone anyway, the only one I can think of that would apply would be gross negligence, but since Apple reviews the Applications they might even have to take the heat for that one.

Presumably the only party that could sue you with some chance of success would be Apple.