I use my little ipod case for everything, and just carry it in my hand. Carries ID, credit card, cash, and I slip my key in, too.

http://www.amazon.com/Button-Wallet-Case-Apple-iPhone/dp/B0088OTAZ6/ref=sr_1_1?ie=UTF8&qid=1362748795&sr=8-1&keywords=livework+iphone+case