Great idea, Bill.
Actually it's my normal road bike, but the back wheel is hooked into a magnetic resistance thingy-ma-jigger. That way it's the same ergonomics as when I'm riding out in the real world, plus I don't have to have two bikes in my apartment!
But what you bring up reminds me of an idea I had a while back: if I can do this with Arduino and my Mac, why couldn't I do it with Arduino and an iPod Touch hooked to the handlebars? I could put a dock for the iTouch in the middle of the front bars, and write a little app to display the info I want on the screen. Could be a neat toy.
As it is, I'd love to find more interesting abstract ways of displaying the data I'm collecting as I ride. For example, right now I'm relying on a 2D graph, but processing could do a 3D graph if I wanted, I just have to figure out what I would plot on the extra axis!