As one way to utilize this flexibility, SEL have produced side-roll and top-roll OLED displays, with the display curving over the edge where a bezel would usually be.The prototypes on show were a 3.4-inch 960×540 pixel display with a resolution of 326 ppi, and a 5.4-inch 960×1280 pixel display with a 302 ppi resolution. They still provide the high color reproduction characteristic of OLED displays.

http://www.diginfo.tv/v/13-0084-d-en.php

This means that software can position buttons anywhere they like around the side of your mobile or tablet. The video in the link is very worth watching.