I believe that the ubiquity of smartphones with GPS capability is an important driver. However at Postmates (I'm a Co-founder), we spent a lot of our time working on our dispatch algorithm, with the goal to constantly improve the way we match the current demand to the available supply.

Our challenges are slightly different than the ones Kozmo faced. One huge difference is that our deliveries are much more distributed since we don't deliver from just one or two warehouses but from locations all over the city. This model brings some advantages but also holds some very interesting challenges at the same time. ;) On a typical day, our couriers operate in the most efficient way during our peak demand times - during breakfast, lunch and dinner that is.