Not entirely true. Apple added developer support for "external out" with 3.2 for iPad, and in the 4.x series (I forget which point release) for iPhone. However, the developer has to explicitly code their application to work with a "second display", which can be a pain.
Apple still refuses to implement simple mirroring (where you see on your external display what you see on your iPhone).
What would be interesting to find out is whether Pioneer is opening the touch interaction API they must have developed for Pandora. If so, that'd make interactive iPhone app development a very interesting
