Hi Manuel. In principle I like the idea. Some questions:
"The widgets would be self-optimizing and always show current products from your store" - how would that work? I'd need to maintain my product database at Product Widgets to make sure its in sync with my shopify stores products, right? Or would it automatically feed my product list into Product Widgets? Avoiding duplication and needing to keep both places up to date with what's in stock would be a big help.
I thought of another scenario. Most of my products I make and sell, but there are some I'd like to offer by print on demand, on sites like spreadshirt and society 6. Therefore, I'd like to be able to embed a widget into my shopify product page, redirecting people to the print on demand version for options I don't have in my premade products. Would that be possible?
Also, you should check out -
http://ecommerce.shopify.com/c/shopify-apps/t/productwidgets-would-you-use-this-app-169623?utm_campaign=ecomu&utm_medium=email&utm_source=subscription#comment-169744 it used to be very good and is similar to what you are planning, but is now mostly orphaned.