NTT DoCoMo is considering using the technology for games and other functions. It was shown running a Rubik's Cube demo where tapping the puzzle from the front and back allowed for complex multitouch maneuvers.
Of course, viewing in sunlight can be problematic, but placing a dark object behind the screen improves visibility.
The prototype will be shown at the Wireless Japan 2012 telecommunication technology exhibition, held in Tokyo on May 30.
Last January at CES, Samsung had also unveiled an almost transparent (40%) prototype OLED panel while operating in a power-saving mode.