This backing for an iPhone features the temperature-sensing material that used to be called "mood detecting," but even if it doesn't spell out if you're happy or sad, it's still pretty neat looking.
Essentially, whenever you hold onto your phone it'll leave a colored imprint from where your hand was, making it a constantly changing and shifting design. And if you want to convince people that it actually shows your mood? Well, I'm not going to stop you. You can snag one of these now for a mere $12.