Check out the Critter Cams! The video didn't load for me on my iPad but worked fine on a computer.
Use this web site with your projector to let students know when their noise level is on the rise. The web site works in Chrome but NOT in Internet Explorer or Firefox. You will be asked to give access to your microphone in order for the meter to work. There is also a free Too Noisy Lite iPad app.
iPad as the Teacher's Pet 2.0
What can a teacher do with an iPad, whether students have them or not? The site includes a downloadable pdf file with lots of websites and apps listed. This is a large file, so it might be slow to download.
Getting More Out of Your Classroom iPad
Image attribution: By Yathin S Krishnappa (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons