In situations where I am concerned about pick pockets (or even being robbed - rare) I use a "sacrificial" wallet. It might contain a 20 or 10 wrapped around 10 or 15 singles. Enough to make a robber think they have enough for their next fix and not enough to cry over if lifted by a good pick pocket. Mine even has fake credit cards - nothing that would fool anyone - except someone in a hurry to get a away. For serious walking, I wear Goldtoe (over the calf socks) and can secret cash in the tops. Don't do this going through airport security