Losing my bag with my laptop would be a huge pain in the ass, but there isn't a lot I can do about that. Losing my phone, my credit cards, & my ID would be a real disaster, & I figured there was an option for me to turn down the volume on that risk. The first photo is my real wallet and my iPhone 4s.
The subsequent photos are my "throw" wallet & phone. Now when I'm traveling on public transit, I carry my throw phone in a pocket on the strap of my pack. I carry my throw wallet in my front left pocket. The throw phone is an old iPod touch I had laying around. The throw wallet is an old ID from TechShop, a prepaid credit card with less than a dollar left on it, my REI member card, & my clipper card.
I carry my real wallet & phone tucked into my belt in the small of my back. Now if someone asks for my phone & wallet I can offer up the throw without losing all my cards & ID.