Could I create an iPhone app that replaces/modifies the default clock screen saver and show something else instead (e.g. my own special clock or whatever)?
How do I go about doing that? I'd appreciate a link to a tutorial on the subject, or to example code that does something like this.
(disclaimer: total iPhone dev noob here)
It's not possible to override any of the functionality on the existing apps/features on the iPhone, including the screen that is shown when the phone is locked. You could write an app that mimicked that functionality when launched, but I don't think that's what you're looking to do.
I think this would be a violation of apples UI guidelines and there is a good chance it would not be accepted to the app store.