Why not try priceonomics they're pretty good for that. With that said nice app!
Locksley, keep up the good work. You need to clean up the results. Removing the unrelated items is desirable. This has a good monetizing potential.
Yeah, I've come across Pricenomics but found their data inconsistent and the sample size too small with ebay results. They're doing good work nonetheless and their front end rapes mine haha. I ain't much of a designer.