I am not sure it would be that complex to develop an iPhone app. The beauty of the iPhone is it is a proper development environment rather than trying to achieve some tie up through html. A simple gateway into the AFPEx system through an app that can provide the required level of security might be an option.
We are developing an app for the ipad/iphone that will display IAP, it might be worth talking to the NATS guys and seeing if there is anything that can be done. I will report back!