The Mission Cycling Wallet is a lot like those iPhone card wallets you see all the time, only this one zips your iPhone safely inside, and lets it face out through a see-through screen so you can read it and use it without taking it out or opening the case.
You can even use it in the pouring rain.
The wallet comes from bike bag maker Timbuk2, and is made from 840-Denier ballistic nylon in the color “algae.” The iPhone slides inside and the wallet closes with a zipper, leaving the iPhone to peek out through the clear plastic front. Around back are three slots for cards and cash, but – as ever with these things – nowhere for coins. U.S. Residents might scoff at this feature request, but outside of your country many places use coins for fairly high denominations: the Euro comes in €1 and €2 coins, for example, with notes not starting until you get to €5 (around $100, IIRC).
The mission wallet, costing $29, is just about perfect for taking on a ride: It protects from sweat whilst sat in a jersey pocket, and lets you carry payment essentials. It also comes with a lifetime warranty, which sounds pretty good to me..