Good artists copy; great artists steal. This quote has been tossed around creative circles for decades and does shed light onto a small fragment of truth, especially among visual artists. The way to master digital design is to take ideas and learn how they were constructed.
Smartphone & tablet applications are small but detailed. To successfully design mobile apps you need to understand textures, shapes, typography, icon design, and color matching. This may seem impossible but if you study other designers you'll naturally pick up their ideas for yourself. The following examples are chock-full of unique interface ideas ripe for cloning & copying into your own designs.