Easiest on the iPod Touch / iPhone using it's "Notes" app, you type in your notes/study guide or other things such as answers you got from someone onto your iPod/iPhone. Then when it's test time, just put the iPod/iPhone in your pocket, slide it out and look at your notes during the test. Just don't be stupid and get caught.
Chris: I'm failing biology. So when we have the test today, I'm just gonna iCheat.
Using your iPod to store notes for an important exam, and then listening to the notes while you take the exam.
Alex: Did you study for Dr. Richard's test?
Ben: Hell no, I'm way too lazy for that shit. I'm just gonna iCheat.