As great as this idea seems, and despite how popularized it is (mainly from movies), keeping a condom in your wallet isn't a good idea. Keeping it in your wallet, where it can get sat on or folded, can lead to the wrapper tearing, or even the condom itself, despite the wrapper looking like it's in tact. It's always best to keep condoms out of extreme temperatures, and leave them in close reach at home where they're safe!