I was thinking about something like this about a month ago. It’s a belt that goes around your torsoe and creates tactile sensations, either through vibration or heat. I’d use it to cheat on tests, by providing me with information I otherwise couldn’t memorize. (Of course, maybe all the time I spent building the belt and developing a language for that belt to communciate in would’ve been better spent studying.)

Looks as if the military’s been working on something similar for a while. Theirs differs in that they’re focusing on remote communication, not cheating on exams.

Links:
http://blog.wired.com/defense/2008/04/darpa-wants-sol.html
http://technology.newscientist.com/article/dn10846-vibrating-vest-could-send-alerts-to-soldiers.html