Project Rubik (Kinetic UI) explored the intersection of the mobile GUI and new physical input methods. The project lead to a series of experiments that looked to answer: "What comes after multi-touch?"
During a brainstorming session in which concentric Saturn like ring were conceived for the GUI, I came up with the concept of a touch-enabled depression on the back of the device to initiate and control the on-screen interface. This later evolved into having a touchpad with stratified rings that were each touch-sensitive and enabled a different interaction in context with the task at hand. This allowed for interactions not restricted to just one app, but across the OS.
This concept has a few implications for single-handed use cases. For one, it means that you can interact with whatever is on your phone's screen without obscuring the view of it with a finger or hand like every single touch-screen phone today requires. Second, imagine if you had limited use of a second hand from an injury or disability? Third, it could me more finite control over a small detailed interaction such as exact scrolling or selecting text for copy and paste functions for example—no more obscuring what it is you're trying to select