Walmart has just launched a new way to pay for your online purchases, with cash. Yup, non-futuristic, non-shiny, regular-old dollar bills. It works like this. You go online to order something, say some towels. Then you drive to a Walmart store and pay for your towels in cash. Once you've paid, Walmart will ship the towels, right to your door. Or someone else's door if they're a gift.