It's an iPad program for teachers and students. If a school has a iPad cart, the iPads are distributed to a class of students and then the teacher uses his/her iPad to push PPt's, movies, documents to the students individual iPads. It's very interactive and the teacher can wait for students to respond on their iPads (questions, drawings, quizzes, etc.) before going forward with the lesson. The teacher obtains a roster of students participating and see how each is doing with the lesson tasks.
Doodlecast Pro allows you to record your voice and your drawing at the same time on the iPad (current cost $3.99). Version 2.2 has gotten mixed reviews, but it might be helpful in showcasing math, for example.
Blog about tools for drawing diagrams--free ones as well as paid ones. I particularly like (Inspiration--$ because you can hyperlink and save as a Word document with hyperlinks too--as well as bubbl.us--free.
VoiceThread is a collaborative tool that allows collaboration online. Responses may take the form of video, audio, doodle (drawing) or typing) and also phone (scheduled call which will record). Many ways to accommodate learners. Highly recommend. Free, but I upgraded to Pro version.