Just some quick links to get you going on this, consider the following interfaces. They are all poised to make a considerable change in everyday experience.
Fingertapps (the multi-touch company)
and of course the iPod touch/iPhone
One of my favourites – brain ball ..
EEG interfaces, as below, or here – the neural impulse activator …
or consider this rather interesting and beautifully simple project ..
or consider the history of the iPod and the Walkman that came before it …
one of the experts on this, Michael Bull, interviewed by Wired.