The Phone Wallet

Case Mate iPhone 4 Credit Card Case, $35
The Hundreds iPhone 4 Code Wallet, $55 

Kill two birds with one stone and combine your phone and your wallet. This way you'll have less to keep track of, and hopefully means you'll be more vigilant about not losing your shit. So don't go throwing your phone on the ground when you get frustrated at Angry Birds. It also helps you figure out what kinds of cards you really need to bring with you when you're not home. So leave that Pinkberry frequent buyer card at home.