Here's a great concept: make student numbers the background on the ipads! Then you can easily see if students have the correct device and also makes it obvious if the students have been changing the background images. (Which they love to do instead of use their device for learning.) I cannot take credit for this idea. It actually was given to me by Michelle Yoder, who found it on this site by a teacher named "Jennifer Magiera." I only made my own collection of them because the East Noble filter was blocking Ms. Magiera's website on the iPads/iPods due to it being a blog. So I decided to just house the pictures myself.
The following document shows the steps to making the numbers appear on the background of the iOS devices: Making iPad Numbers on the Background.