Backstory: I was out a local bar this past weekend and had a really tasty cider. I took a picture of the cider to buy it for myself later. Come to find out the two liquor stores near me don't carry it. One offered to buy it and have it shipped but I wanted it now :) For reference, I live in Maryland, USA. We have specific stores that sell beer/wine/liquor, it varies state by state.
The Idea: Snap the barcode or label of a beer and the app would tell you where to buy the beer.
Deep Dive: With the increase of craft beer and ciders it's becoming harder to find random beverages you try at bars. If there was a way for a local brewery to support the app, it would help give them exposure by being available in stores near bars that carry their beverages. This would allow breweries to expand into new areas one bar and liquor store at a time. Distributors would want to coordinate with both places to help gain new fans.
Validation: I still want to find that delicious jack's hard cider, someone build this for me!
Monetization: The data aspect on this with grouping liquor stores and bars geographically would be appealing to distributors. Also, if you gained enough traction on this app, untappd, the most popular beer drinking app may look to buy you out.