Tom - for some reason this link isn't working for me, but the one you posted to your status is.
Thanks for sharing this! We are actually working on tutorials to teach everyone how to do this. Try going to the video tab and uploading it there if you get a chance. That would be a good way to share it as well.
Haven't got my document camera yet - but really looking forward to it (I may have to lock it down so my colleagues don't nab it! :-) ) I think this is a good idea - I didn't watch the entire lesson, but it would be good to do especially if it's a difficult concept. I can see myself using this to record mini-lessons when I have a sub. I have on rare occasion done videotapes when I've been gone - but found I also had to run notes off for the students. This way they can see clearly what you're writing, and hear your explanation. I like it!