Google is putting up half a billion dollars so you can do your grocery shopping from home.  The search engine giant is investing $500 million in Google Shopping Express.  

It's a same-day grocery delivery service that will link your home computer or handheld device to supermarkets, grocery, and discount warehouse stores near you.  That contrasts with Google's main competitor, Amazon Fresh, which delivers most of its groceries from Amazon's own warehouses.  

Google Shopping Express will launch for free but will eventually be a flat-fee membership service, similar to AmazonFresh Prime.