Here are some screen dimensions and iOS GUI element dimensions for the iPhone 5. There didn’t seem to be one clear source so I made one. I’ll add iPhone 4S and iPad later. I hope you find it useful. More info on my main site at Appmockuptools.com.
And here is a chart that lists all of the iPhone 5 dimensions out including Nav bar, Tab bar and Tool bar, buttons and icons.
App Mockup Tools 