I think it is time for the OP to come clean about his reasons for doing all this.
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.