I just received notification that ShowMe was available for download so I went ahead and downloaded it. ShowMe is a basic screencasting app for the iPad... and it is free. It allows you to mark up a whiteboard with six basic colors and a single line thickness. It also allows you to import images from your photo collection and annotate on top of them. It gives you an eraser to erase your pen drawn annotations as well as the ability to import additional images during the recording of a single screencast. However, once recording, the only way to delete those images is to wipe the board clear/clean. It is not possible to manipulate the images once you bring them in to the app.

I recorded the following trial that lasts 3:11. It recorded without a hitch and uploaded to ShowMe site in under a minute. You do have to create a free account at ShowMe's site to be able to share/publish. The app itself gives no way to export recorded projects in a more universal format that can be imported into other applications for further development. It does provide multiple ways to share your projects as indicated in this screenshot below. When you publish, it also sends you an automated email with the direct URL of the screencast, which is nice.

Here is the actual screencast that I created and embedded with the supplied embed code. You'll also find some examples at the ShowMe site.

I think such a tool has the most impact when put in the hands of students, not teachers. Sure, teachers can show things... but that's what teachers do all of the time while kids sit passively listening or watching. This becomes a great tool for students to show and share things that demonstrate THEIR learning/comprehension/skill/mastery... and yes, even misconceptions... and places responsibility on them to actively make their thinking known.