Currently I’m exploring various apps for live annotation and presentation to a classroom. We’ve got a test instance of Tegrity (a lecture capture system). One key aspect is that it captures the presenter’s podium computer screen.
I’m experimenting with AirSketch, which allows the instructor to draw on her/his tablet, on top of photos and PDFs. The app provides the IP address of the iPad, which you enter into any HTML5 compatible browser (Safari, Chrome, Firefox). The browser then updates in real time with what is being drawn on the iPad. We then capture that browser with Tegrity and voila! Remote annotation!
My current favorite is Audioboo, a great app students can use record and share reflections. They can comment on other students' reflections. One strategy (called AudioMo) asks students to record a boo everyday for a month, reflecting on what they are learning. At the end of the month students can record a metaboo where they summarize their learning. Boos are limited to five minutes in length. You can even find Audioboos in iTunes.