Walmart is signaling its commitment to autonomous deliveries with a new investment in self-driving company Cruise. The two already have a cozy relationship, having recently worked together on a delivery pilot in Scottsdale, Arizona. Walmart was so impressed with Cruise's "differentiated business, unique tech and unmatched driverless testing" that it decided to take part in the GM subsidiary's $2.75 billion funding round. The investment will see Cruise become an important part of the retailer's "last mile delivery ecosystem" -- industry parlance for the final journey from warehouse to customer. Walmart has struck additional partnerships on driverless deliveries with companies including Google's Waymo, Ford and Udelv.