While I understand that in order for an iPhone application to be accepted on the App Store, one requirement is that only documented libraries are to be used.
If this
You might want to check out a classdump of apple's private framework headers. Run this perl script:
http://arstechnica.com/apple/news/2008/11/dumping-the-iphone-2-2-frameworks.ars
and navigate to the PhotoLibrary directory under PrivateFrameworks. Some of the classes in here look pretty promising for direct camera access.
Using the undocumented API could hurt your chances of passing through the app store, but it's all very subjective - If your product is good, apple will probably let it slide through. I'd recommend making friends with a developer evangelist at Apple.