How exactly do I identify the product I want to purchase? There can be many slightly distinct versions of the same product on amazon. It sounds like I would have to pre-select the products that my users would be purchasing, because for them to search for what they want they'd have to use the amazon website anyway.

I'm just having trouble seeing the value in this, except for the very specific use case of regular, event-driven, identical, automatic orders (eg, I have my lights hooked up to an intelligent system that notices that the bulb blows out, so it then submits the pre-prepared order for the correct bulb via zinc.io).