Actually - not completely crazy - how willing would you be as a passenger to take a few detours to get a saving on your taxi bill?
I'm actually curious if anyone knows how well Uber Pool is working? I've never used it for a few reasons, but a big one is that I don't want to risk another rider pickup causing me delay in getting to my destination.
Maybe something like milkthemiles.com - make the retailers agree to your demand pricing not the inverse (tm)...
http://techcrunch.com/2015/04/28/uber-is-quietly-testing-a-m...
The problem would be making sure that people can easily find their packages, and that they don't steal others' packages (which would be easy to check)
If you have a bunch of parcels in the boot of your car you deliver them when you are nearby on an Uber call or when you have no uber work.