Jeffrey Han showed off a gestural user interface at ETech in which the user hands manipulate object on a desk. It's based on Han's multi-touch interaction research, which applys a form of biometric input. Frustrated total internal reflection (FTIR) acquires true touch information at high spatial and temporal resolutions, and is scalable to very large installations, according to Han's site, which has some good demos.
Han's demo, using two fingers to move and manipulate objects (or using all fingers on a virtual keyboard) got me thinking about Minority Report (if you saw the movie), where Tom Cruise uses his hands to manipulate objects on a large screen, but doesn't have to touch it. Han said that touching the surface offers more precise manipulation and is more intuitive than gross gestural interfaces a la Minority Report.