One of the most useful apps I've seen in some time is EduCreations. This app allows teachers to create and share video lessons with an iPad. It is the ultimate in user friendly. I recorded a math lesson within 5 minutes of opening the app for the first time. It records your voice and your writing so that a student can watch and listen to your instruction as many times as necessary to understand a concept. Follow this link to see a
lesson like the one shown below: http://www.educreations.com/lesson/view/subtracting-fractions-with-like-denominators/728785/
Best of all, this is is totally free!