Do the reviews appear anywhere else on the web? Are people leaving reviews on the reviewer's site, and they're visible there, and then you're pulling them in via this widget? Or are they only visible on your site, through the widget?
If the reviews are elsewhere on the web (for example on a review site such as Yelp or Angie's List), Google is going to understand that that content belongs on that site. Pulling it in via this widget probably won't send much in the way of a unique content signal; it's unlikely that it would be seen as duplicate content, though, as long as the page it appears on also has its own unique content. Appearing through the widget also means you likely won't be able to mark up the reviews using schema.org.
If they appear somewhere else, and Google can easily associate those reviews with your product, you'd probably be better served having a function on your own website where people can review your products there. Then, let those reviews live on your site, and the third-party reviews stay on the third-party reviewer site.