PHP Service/Flex Question for Dolphin

This isn't a Dolphin specific extensions question, but I figure the best place to ask would be here where there are more development types. :)

I've begun developing with Flex, focusing on Android devices with the AIR runtime, and I'm using Flash Builder Burrito release. I want to try my hand at making a simple app that can retrieve user information from a Dolphin site for a client but am unsure which file or files I would connect to for the Data/Service to handle Service Calls. Any ideas?

There is an xmlrpc file that is used by the iphone, and I think the desktop app. This should provide a good way to access the 'back end'.

Speaking of the desktop app, that may be the best place to start.