When you play around with Google Earth, you discover you can locate all the pizzerias around your house. You can then click on a pizza icon and get the pizzeria's local info. Utilizing Google Talk and Google Checkout, theoretically, you should be able to talk to and see (just like on Skype) the pizza guy in the pizzeria, order a pizza, pay for it, and have it delivered. Google, via Google Checkout, will get a cut of the pie, so to speak.
This would work with clothing stores, drug stores...any kind of retail store.
I believe Google is working on this. All the parts are already out there. And when Google announces this, there is no limit to how high the stock can rise. Their current ad business will pale in comparison to this.