Yes, the post office actually has offered the concept of "general delivery" since almost forever. I presume DHL keeps the savings of not sending out trucks. My vision is a system that's cheap enough, and fast enough, to deliver a gallon of milk if need be. It should work well in urban areas, and in fact could even be adapted to the denser suburban locations, though it's harder to get enough of the population within say, 600 meters of a depot so that they consider it a quick walk. You also want enough volume of orders that it justifies a delivery every few hours rather than just daily, which may never be possible in less dense areas.