Startup Idea: E-commerce Best-Seller Mining Software

Startup idea to develop a software that extracts data of best selling items from major e-commerce sites like eBay and Amazon. This would help e-commerce website owners to decide what to sell on their website, thereby saving their time on manual research.

I run an eCommerce website. I need to know the best selling items on all major sites such as eBay and Amazon so I know what to sell on my website. I would like a piece of software that can pull this information for me from all sites which would save me time researching it myself. Yes I would pay for this software.