Here's Shopper in action. It's not clear whether it 'scrapes' the main Google Shopping pages or whether it uses an API, but it does seem to work:
About a dozen countries/markets are supported - the dialog above scrolls(!); (right) the simple main menu - 'history', obviously, remembers what you've searched for, so that you can search again in the future.
Let's try a few searches. "Nokia 808" brings up the usual Google Shopping list of variants - as usual with duplications, but this isn't Shopper's fault; tapping through brings up the description of the item in Google Shopping's database.
Now to the list of vendors and prices. Quite a range - that DigitalRev.com price looks tempting; (right) tapping through brings up the vendor's web site with full details and ordering information.
Let's try another search, for a printer...
Again, simply pick a vendor and price and then tap through.
A helpful and competent front end onto a surprisingly useful Google consumer service. Certainly worth a quid in terms of the money it may save you when looking for something you know you want.