Play iPhone / iPod Touch music on my AirPort Express via WIFI

You're absolutely right. This idea has a lot of demand and traction in the iPod Touch / iPhone community, but as of yet, there is no viable solution. The current workaround (using the "Remote" app to control iTunes, which them serves media to an Airport Express) is clunkly and requires too many steps.

One company, Rogue Ameoba, which develops extensively for Apple integration, has recognized the significant demand for such a product, but it claims that it can't develop an appropriate app because it would violate the developer/SDK agreement Apple requires developers to consent to. The website and an interesting post can be found here:

http://www.rogueamoeba.com/utm/2008/1...

As an aside, the reason people jailbreak their iPhone and iPods is because Apple won't listen to reasonable requests from developers who would like to develop useful SDK & Apple Store apps like this. Many people would pay handsomely for applications that are are totally benign.

If there's an App Store (i.e., Apple-approved version) or jailbroken version of this software floating around, I'd love to see it. If (and it's a very big if) one is developed, myself and others would gladly pay for this functionality.