You clearly haven't read any post in this thread. Your app doesn't solve any of the problems mentioned and as said before by the OP, does more harm than good for Vendors who focus on the European market.
For Shopify to track the acceptance they would need to attach that information somewhere. If the Customer is not logged into an account, then its anonymous Information. Also (and i'm not sure why) not everyone uses Google Analytics. In Addition to this, since Cookie bars are not default, its hard to force the information.
The Above link shows how to add Custom Collection of Information, and could be attached to your "Accept" Button. You could make it a popup as well (like Age Verification) saying if they do not accept, they can not enter and have it Redirect to another site if they say no. But Again this would need to be setup on a per use basis since it could change from Theme to theme, or app to app, not to mention the custom settings in Google Analytics.
I will see if I can get the Basis of it setup in my cookie bar. Right now I use Facebook Tracking in it (optional, and experimental) but I will see if I can get mine setup accordingly. Its a very fair point seeing that they can call for proof. Being in Canada, and serving Canada and the USA with my stores its not something I had to dig into much myself. But I will try to get my Code updated.
Thanks @finnhartwich - agreed it sounds like another 'more harm than good' app :)
Note you don't have to 'focus' on the European market for GDPR to be relevant. You just need to have at least a few customers in the EU... and Ecommerce News claims 'Ecommerce sales in Europe grew to 621 billion euros in 2019' - so chances are very good that you do have some!