Is it possible to display the iPhone Unique Device Identifier number in the main settings/preference screen outside of the application?
If so, how is this done, as I can't see how to pull the UDID into Root.plist.
If not, I'm able to display it in a normal iPhone Application view, correct?
I don't understand what you mean by displaying it "in a settings/preference screen". Is this a screen in your application? You can get the unique identifier from [UIDevice currentDevice].uniqueIdentifier and you can use it anywhere in your application. So if this screen is in your application then of course you can display it.
Yes... this is possible!
you need to create an app that will store values to iphone settings page. (google about it)
you need to get the device guid. here's a link http://blog.timeister.com/2009/06/25/objective-c-get-iphone-device-guid/
Adrian