This idea has been around for quite a time now, and I was referring to it in my Contemporary Aesthetics in Digital Architecture course - so it seemed sane to take a little look at some of the players of today.
Probably the most famous wearable computing guy, Steve Mann has been driving the idea of how to integrate digital technology into what we do. Iron Man (love the film) is an ultimate form of this augmentation of the physical, sensory and even intellectual (through the AI). Anyhow, Steve Mann began with much simpler bits taped and strapped to his head and body which has evolved a great deal since 1980 when he started. His site, WearCam, has some good resources and coverage of his work over time - plus plenty of info on his water-based musical instruments.
[Steve Mann's evolving wearable computers from the Wikipedia entry]
Check this article on space.com by Brian Bergstein and this interview on youtube (ignore the presenters and check out the billboard swapping).
There are others exploring this field of course (apart from cinema)
Lets let BMW have the last word for now: