Teraokaseiko Co Ltd just exhibited a display that has touch sensory input on both sides. In other words, it is a two sided touch screen display. The transparent material used allows you to see straight through it if you want to see where the person on the other side is touching the display. Possible uses of the technology are abundant, but the two obvious ones that come to mind are gaming and use with maps.
"Teraokaseiko Co Ltd exhibited a touch panel display that can be operated by touching either side of the display at Sign & Display Show 2008, which is taking place from Aug 28 to 30, 2008, at Tokyo Big Sight (Fig 1).
The display was made by attaching a resistive touch panel to the both sides of a transparent inorganic EL panel developed by Teraokaseiko."