Why?
For the customer, it’s a fun way to get better service, deals, and other benefits. For the retailer, it’s a wealth of new information they can use in their sales funnels.
How?
An augmented reality app. The customer points it at different items in the store and immediately gets extra information about it: reviews of other shoppers, how many “loyalty points” will he get for buying it, is there a special deal on it only for loyal customers (or only for him based on his profile), what are similar items that he might be interested in, etc. This is very similar to shopping online in that the customer is constantly giving the retailer feedback by every action they take, every item the seem interested in. It brings the benefits of online shopping to both the customer and retailer.