Here's an idea that occurs to me frequently when making slides for conference tutorials. Sometimes I make a slide and I know that it might be too advanced, but it's a crap shoot. If the vast majority of the audience understands the slide, I can save several slides by not explaining it. If enough people look confused, I want to display those slides. I don't mind making the slides up front, but I'd like to be able to only show them if I think it's needed.
I wonder if there's some way to make good Keynote triggers that would let me
say something like: "if you want to explain why
1 + 1 = 1, press F1;
otherwise, press Next."
Choose your own slideshow.
I also wonder whether the Visor program that I saw ages ago is triggerable during a slide show. It looks good, and it would be convenient to keep a giant-font terminal ready to slide down to demonstrate answers to hard questions.