Shopify has a review App. When you use it in a shop, you can display reviews. Since you control the placement of the reviews, you are in a position to also inspect the reviews from DOM perspective and decide the latest, and what the markup looks like.
Since you know the markup, and you have access to the Shop, you can scrape the latest review using any screen scraper you want to use. With that, you can easily have each products newest review sent back to the App you installed in the shop. Using an App Proxy, you can do a callback asking for the details of the latest review, if any exist, for re-display any way you want.
Sure that is convoluted and weird, but you can do that.
