Zen Cart Plugin

I need an addon to Zen Cart that helps me distribute license files to my software products. Specifications: 1. Allows admin to associate a few variables with any product in the Zen Cart DB (used for generating the license file) 2. Allows customer to associate his product purchase with a domain name (used for generating the license file) 3. Gives the customer a link to download the license file (will provide the functions needed) 4. Admin interface for changing the admin/client variables mentioned above 5. Be very very easy to install on any existing Zen Cart installations