My geometry students recently did their 2nd video blog. I assign them each a different proof and they create a diagram and explain how to prove. See two of my favorites from this year and the prompt below.
1. Must be typed, including diagram, symbols and tick mark notation (I suggest using Google Drive's Drawing App)
2. Must use a screen capture tool like jing that will record your voice and your typed completion of the proof
3. Must be embedded in your blog
4. As always, creative title and 1-2 sentence introduction