I'd like complete pricing data for common purchases including both brick and mortar and online retailers. Eventually, I'd like a web site where I could enter my

I'd like complete pricing data for common purchases including both brick and mortar and online retailers. Eventually, I'd like a web site where I could enter my regular purchases (groceries + household goods) and it would tell me the cheapest way to acquire them (e.g. buy this list from the local supermarket, these items from walgreens, and order these 3 things from amazon). Obviously, the pricing data would need to be up to date esp. with regards to sales.