I've been hoping someone would build the same thing. Even without delivery, I'd love to be able to search for products across multiple stores through a web interface and see their availability in a map view, with price and in-stock status. I would be happy to go to the store and buy it, as long as I only need to make one trip and I know it will be in stock and at a certain price.
I worked on this, it was called Milo.com. we had crazy scraping and xml/csv feed ingestion. It was a terribly difficult business because most retailers hated us. ebay bought it and eventually killed it.
Why did retailers hate you? Wouldn’t they want a solution that brings people to their store because you listed their product as being there and available?
That's a big part of it, yes. Retailers take advantage of information assymetry after all. While you're in Best buy, you may pay more than online to walk out with an item, but would you pay more if you could instantly confirm it's at Walmart next door for $20 less? Maybe not.
Funnily enough though Best Buy loved us and provided real time data via API and daily CSV data dumps just for us. They were like that, along with Toys R Us and AutoZone. Most others hated us, including Guitar Center after we accidentally DDOSed their web site with our scrapers.
