Aggregated retail sale data, pushed to user via GPS-trigger

Envisage an application that aggregates retail sale date and location information and combines this into a simple, clean UI that reflects what nearby sales are local, upcoming and tailored to pre-set interests be they fashion, tech, food, and so on. Retailers will buy in because it means they can potentially meet a larger audience without the cost of advertising. Users will buy in because everyone likes a sale, but in my eyes no one knows when they are. I don't believe there is currently a platform that does this, on mobile nor the web.