When Apple first announced the iPhone, there weren't many multi-touch systems on the market. New York University had released a dramatic demonstration video of the results of its research into multi-touch interfaces, but few such systems had made it into practical use.
In May 2007, however, Microsoft announced Surface multi-touch computer system. Surface uses cameras and light for its multi-touch interface. Surface should hit the market in winter 2007.
clipped from: electronics.howstuffworks.com 
