I think their is definitely a market for this. My question is, isn't Uber doing this already & has much more sophisticated logistics infrastructure in place? Uber Pool (future potential) = efficient pickup of parcels / deliver - on-demand.
First of all, you're wrong. Uber also has an API, which is for another kind of user, but it's still an interface that enables selected developers to access all of their functionality.
Second, what makes you think Uber couldn't create a new app that connects to the same backend in under a month? There is no such thing as "permanent advantage" (or some companies would live forever), and there sure as hell is no such thing as an advantage based on UI.
I agree with the first part of your post, but... I have quit all kinds of services for a competitor because of a shitty UI. Now that being said, I think having (and not being able to escape) a shitty UI is symptomatic of more intrinsic problems. But there is a business advantage.