Walmart is unveiling a $50-a-month membership service that lets harried shoppers use text messages to order items to be home delivered. Jetblack marks the latest effort by the nation's largest retailer to cater to higher-income shoppers. It's being tested in Manhattan and parts of Brooklyn. The service will offer same-day and next day delivery at no extra charge. It allows shoppers to order everything from birthday gifts to household essentials based on curated shopping recommendations. The everyday items will be sourced from Walmart and Jet.com. For specialty items, Walmart is working with stores like Pottery Barn and Saks Fifth Avenue. The service, which is currently invite-only, is being led by Rent the Runway visionary Jenny Fleiss.