Screenchomp (https://itunes.apple.com/th/app/screenchomp/id442415881?mt=8) or Doodlecast Pro (https://itunes.apple.com/th/app/doodlecast-pro-video-whiteboard/id469486202?mt=8) - We have started using this to assess our own writing. Children can take a photo of a picture they have drawn or some writing they have done and talk about it, showing what they did well and how they could improve it.
iMovie (free App on new iPads) - children are learning how to use this to create their own movies.