Re Shopstream, seems like a terrific idea. How are you planning to market it? Suggest you integrate with the Shopify platform first, as they really care about and market the apps in their app store: http://apps.shopify.com
Hey. ShopStream is not my own application. It's the app I did for one of my clients. BTW, it's integrated has Shopify integration and is listed here. http://apps.shopify.com/shopstream