I'm glad to know that we're going to get some iDevices. I have an iPhone and an iPod Touch, my wife has an iPad - so I'm quite familiar with the devices. I'm glad to know that you can freeze the image to keep it from rotating. That could be important in music reading situations! It will be nice to be able to sync all the devices together.
When we check out microphones, metronomes, tuners, etc. - we ask the students to leave an item as 'collateral'. This can be something like a wallet or a cell phone. They get it back when they return the borrowed item. We will probably use this system for the new tools as well.