The iPhone display is covered by Corning’s Gorilla Glass (not sapphire). The iPhone 4S’ TouchID sensor (the home button) is covered by a small synthetic sapphire pane. However, given Apple’s substantial investment in GT Advanced, the company might use sapphire for larger panes in the future.
Make that the 5S’ home button/TouchID sensor. Plus the outermost element of the rear camera lens is rather sensibly sapphire, IIRC.