I'll wait to see what the feedback is, but my first thought, at least for nyc, is that why would anyone want to use this? Unless the truck is a couple of blocks away, it'll take a while for the truck to get to the user requested location. In NYC, there is a drug store every other block. So it'll take 5 minutes for anyone who wants an ice cream to go to one and buy one, instead of waiting for a truck. And how much is uber going to make on selling ice cream (I imagine that if something like this is successful, they'll expand to other products too..)
They might be able to clean up by becoming an outsource dispatch service for air conditioner repair in the southern US. Timely response is critical for both repair contractors and their customers.