The last time we wore a mood ring the cute boy next to us casually leaned over and said to our geeky 13 year old selves, 'It's black. That means you're horny.' Much to our horror (how did HE know?!). Get that same excitement from the back of your iPhone with the Laserworks Heat Sensitive iPhone 4 Backing ($12). With heat sensitive technology you're phone can now tell you when you're angry, peaceful, stressed, or, as usual, horny.