Walmart has introduced its answer to Amazon's one-day shipping for Prime subscribers. The retail giant's NextDay delivery offering is rolling out in Phoenix and Las Vegas today, May 14th, and will be available for online customers in Southern California over the next few days. It's more of a curated shopping experience than an option shoppers can choose for any item on Walmart's website. But so long as they find the products they'e looking for among the 220,000 items listed on the portal, Walmart's might even be a better deal than Prime's. It's free and requires no membership, after all -- they just need to meet a $35 minimum order.