I'm a professional Shopify App developer. I've made several custom apps that are in use with satisfied customers.
I'd like to understand your post a bit better. What do you mean by scan them on and off (back to supplier)? Would you like to scan product SKUs and make them available in your online store? Are you doing some kind of return to supplier? We have the perfect cost effective solution for you once we have a solid idea what you're looking for out of an app.
Sam - Owner @ AchieveApplabs