I purchased many security related items for a trip recently and the one I used the most was the Eagle Creek Leg Wallet.  It was way more comfortable and better hidden than the money belts, and spacious enough (unlike some of the smaller arm/leg wallets) to hold passports plus money plus credit cards.  I really did forget i was wearing it at some points because it was so comfortable.

I pulled my sock over it to prevent it from accidentally slipping off, although I don't see how that could have happened with the solid Velcro fasteners.  It definitely should be considered more of an above the ankle wallet than an upper leg wallet. I went through some notorious pick pocket areas and never once felt in jeopardy of someone getting at my Leg Wallet.

IMO, a must have for trips to areas where pick pockets roam, and anywhere else where you wish to carry around important smaller items.