Pencast experiment

I have a new gadget - a Livescribe Echo Smartpen. It allows me to record what I'm saying and what I'm writing. Typically, these are used by *students* to record their lecturer; I'm trying it out in reverse. I plan to record solutions to questions that students bring me during office hours, so for those of you who don't have the time can get the same teaching experience as those who do visit me. The explanations of particular problems will be delivered in the form of a playable pdf file, and in today's case, you can hear and see me solving a problem that asks how many photons of microwave radiation does it take to heat up a small cup of coffee. Feedback on how useful (or not!) you find this is most welcome; it's very much at the experimental stage.