Since few shoppers can wait for Amazon to ship their gallon of milk, smartphone usage in grocery stores is an entirely different beast than in big-box and electronic retailers, where the "scan and scram" phenomenon of price comparing runs rampant.

Consumers aren't price checking against the Piggly Wiggly down the street the way they compare the values at Target vs. Best Buy, so mobile apps are popping up as tools for shoppers to find manufacturer deals and make lists as they trawl the supermarket aisles.

Food and medicine are the categories that see the least smartphone usage for research and shopping, according to an online survey from Omnicom Media Group and Microsoft. Phones are used more for shopping for entertainment products, restaurants and consumer electronics.