It's being widely reported that Google's metashopping site Froogle now lets shoppers see what items are available at physical stores nearby.
Coverage seems quite weak at the moment. Here's a search for "earrings 94301" that returns almost no results in the Palo Alto area. I would hope that would improve quickly since the service is nearly useless as is.
However, looking forward, this brings Google much closer to the disintermediation threat that has struck fear into retailing giants. Improve the coverage, hook this up to Google SMS, and you've got a service that might "be able to tell Wal-Mart shoppers if better bargains are available nearby."