If only they developed an on-line store and a delivery mechanism. It would be the optimal solution from the customer perspective (price, feature and distance). Thanks in part to the ubiqutious internet.
On the vendor side of the app, you'd have a list of orders and a map of the customers. Done properly, this could be a big win for vendors, since ordering would be easier, increased volume would be likely, and they would be better able to plan production/delivery.
Basically, it's like Loopt but for hyper-local b2c. Instead of hooking up singles or friends, you're hooking up cart vendors and their customers.
One way I could see working is a widespread existing business collection/franchise spreading out into more and more products over time - so companies/organisations as diverse as interflora or starbucks might start by offering products in their core competancy online, maybe start allowing other companies to join the scheme to cover gaps in their coverage, and eventually spread out to cover a wide range of goods so the website/app grows beyond the original founder.