Develop a chrome and firefox extension that detects amazon purchase

Since amazon does not have a buyers API we need a chrome and firefox extension that can retrieve recent purchases that the user has made on [login to view URL], or every time a user makes a purchase on amazon and send certain information to our app, the user has to log in to our app (the extension must also handle that). Background: we are a freight forwarder company, our clients mostly purchase on amazon(so we will begin here), and we need them to "tell us" certain information about their purchases, for example: final price (after tax and shipping), tracking number, carrier, etc... Currently they should log into our system and create what we call a "pre-alert", however, only a very low number of customers do it. We want to implement an "automatic" way for them to create a Pre-alert only by installing this extension. The extension should first log the user into our system, with our API, and detect when a person makes a purchase (we will later would like to add other stores: walmart, victoria secret, etc...) and send the information we need to create a Pre-alert for that user.