Here is a robotic finger for smartphones that lets you do more with them. The MobiLimb is a 5DOF robotic limb that can work with most modern smartphones. It enables them to move and interact with you. For instance, the MobiLimb can touch you as you get a notification, act as a stand, or simulate emotions.
Touch is detected on the surface. The angles of each motor are detected to allow manipulation. The MobiLimb can also work as a smartphone joystick.