Back when I was in high school (as if it was really that long ago) we had a discretionary rule on iPods, phones, et cetera. It was up to that particular teacher to say yay or nay. My teachers didn't mind if you listened to music while working individually, but playing games or texting was verboten.
However, whenever someone had their phone taken away, the teacher wouldn't mind if they took out the battery or memory card. Granted, that's considerably harder on the iPhone/iPod, but it still goes to show that a teacher doesn't need to be accessing the device or using it in any way, shape or form.
In fact, the only time I've ever seen a teacher use a student's confiscated device was during my sophomore year when a teacher actually called a kid's mom because it was the fifth time he'd had the phone taken away.
Best part? The teacher called her in the middle of class and put her on speakerphone. The kid wasn't very happy but you can bet he never used that phone in class again.