If you or a lady you know is not fortunate enough to have cleavage sized for stashing cash, phones, and plastic, I recommend a boob job. Or, I suppose, a JoeyBra. JoeyBras are designed to provide hands-free storage of a girl's necessities without sacrificing sexiness or comfort.
I mean it when I say necessities though. Money, ID, credit cards, phone, keys. None of that 8 different boxes of makeup, 3 scarves, and a full-length mirror malarkey. Think of it this way: JoeyBras are for minimalist girls who like to got out and have fun and be cool without a bunch of shit, such as hair products and emotional instability, weighing them down. You know, the kind of girls all guys would like to find. The 5-8s on the Hot Crazy Matrix.
JoeyBra's stuff stuffing bra says it will safely store any item that fits in its side pocket without changing the way the bra fits, and regardless of bust size. When empty, the pocket is essentially unnoticeable.
JoeyBras come in colors Black and Leopard and are slightly padded with a push-up style. Straps are adjustable and convertible. JoeyBra also makes sports bra versions of their chest purses, viewable here.