Even if you're adamantly against putting a case on your phone, you might make an exception for the FlexCase being developed by the University of Applied Sciences Upper Austria and Microsoft. When opened, it doubles as an extended touchscreen for your device that can also be flexed for unique ways to interact with your phone. Instead of having to use two-fingered on-screen pinch gestures to zoom in on a map, users could simply bend the corner of the case's cover forward or back for quicker navigation. Piezoelectric circuitry inside the cover is able to detect touches, squeezes, swipes and exactly how it's being bent or warped. All of those gestures can also be translated to shortcuts or other alternative ways to interact with an app.
Imagine quickly navigating though an ebook by grabbing and bending the edge of the case, not unlike how you'd grab the page edges in a real book to flip through it. And because the cover integrates its own low-power e-ink display, it can serve as an extended screen for your smartphone. Copied clipboard contents could be left visible for quickly pasting between apps, or you could leave a map with directions on the cover, allowing you to respond to an email while still keeping tabs on where you're going.
For the time being, the FlipCase is just a research project that will be presented at the Computer-Human Interaction conference being held in May. (Hence the awkward cables hanging off the bottom of it.) But eventually the technology could make it into our hands as smartphone cases become just as useful as the devices themselves.
Besides, there's no such thing as too much screen space when you're trying to work on a computer designed to fit in your hand.