I have just read in the latest DrDobbs (can’t find the article online) that doing C++ on the iPhone is really not such a big deal. Being completely ignorant about all things Apple (the only device I own is the Shuffle), this was rather surprising for me.
iPhone software is usually written in Objective-C. The framework you use for writing your applications (Cocoa Touch) is pretty powerful and Objective-C (especially 2.0) is a nice language. And, you can mix in C++ wherever you want (e.g., write portable application logic in C++, and only the GUI layer in Objective-C, using Cocoa Touch). From a quick glimpse at the iPhone SDK it should be easy to port POCO to the iPhone (it’s basically Mac OS X, so not much porting necessary).