I decided that we need to do that on the web, too, so I build a virtual keypad, using HTML5 video and a webcam.
I think there’s a fair bit of potential for video based interfaces. I’d like to see a combination of this and the HTML5 drumkit, for example.
You can try it out here: http://demo.nicklothian.com/keypad/. You’ll need to be using Firefox 3.5+.
Here’s a demo video (ironically as an embedded flash video):