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There are three apps that I find useful while shopping that require scanning of items. Jingit, CheckPoints, and ShopKick

The second, Shopkick is also an app in the AppStore. It is used by locating stores in your area and then scanning the items barcodes with your phone. The bonus of this app is that you can like things and make books of the items you like almost like a Pinterest type of thing. Another reward you get by using this app is what the app calls "Walk-ins" which are points awarded just for entering a participating location, these are usually large retailers like Walmart, Target, Shopko, and many others.
Saving the best for last, my favorite of the three is CheckPoints, this app like the others is used by scanning barcodes to earn points. But the really interesting part of this app is the lotto, you can earn tokens, to play the slots or scratchers, by either scanning items or buying them with your points. The largest prize you can win is worth around 500$ worth of points.