I spent part of the weekend writing an application that lets me control Keynote with a Wii Remote. It's called Wiinote and it's available for download. I'm not sure where I'm going to take Wiinote; while it does everything I want, I could see how putting some more work into it would result in an application lots of people would find useful.
So, please, let me know if you find Wiinote useful, or what you'd want to see added to Wiinote to make it useful for you.