If one of your friends has always been the one constantly losing keys, I am ready to bet, from now on he will definitely keep an eye on them, since right now together with keys he will lose … cash. The following option is included in the Cash Stash Keychain (more than $8). Your cash (everything you can put in a waterproof capsule) will always stay safe and sound. Don’t worry – the capsule is made from aircraft grade aluminum and it is a completely waterproof one. Your friend will always has some cash!