Here are some resources that may help.
Here are some apps that we like:
Kahoot.it (free) – Turns mobile devices into a clever student response system for the classroom.
Noteability ($2.99) – A note taking app that allows you to annotate PDF documents and will also record audio.
Explain Everything ($2.99) – A powerful interactive whiteboard app that can annotate documents from Word, Excel, PowerPoint and PDF. You can also put together screencasts (a recording of what you are doing on the screen along with the audio) which makes this app perfect for quick instructional videos.