Need inputs: Talk on usability

Hi folks, I have been invited to talk about usability to a bunch of people that are training to be technical communicators. The duration of the session is two hours. I don't want it to be a 'words only' session. Of course, I would be talking to them about the basics, the importance of usability, standards, product design and usability, and user-centered design. What I am thinking about is some kind of an exercise, a practical session, for the participants. I was thinking if I should ask them to run a quick UI review on their mobile phones (and take it from there... UI standards for mobiles, gloss vs. Utility etc.).
If you have any comments suggestions, please leave a comment.