Research on touch screens didn't end with the Apple iPhone. Microsoft's Patrick Baudisch, who's also a professor at Potsdam University in Germany, has developed a prototype display the size of a credit card, with a touch pad on the back (left). A cursor indicates the position of the user's finger, but the tiny screen remains unobstructed.

At the opposite extreme, Jeff Han of Perceptive Pixel in New York City is using his large touch screens' pressure sensitivity to create new graphical interfaces. The screens made a splash during TV coverage of the 2008 election, as news analysts panned across maps by swiping the screens with their fingers. Light travels within an acrylic pane overlying the screens. Touching the pane scatters the light, indicating the point of contact and the pressure exerted. Han has developed software that lets users manipulate on-screen data in three dimensions rather than two, sliding virtual objects under each other by pressing down on them.