Sendy woudln't be the Mailchimp killer without a proper Shopify integration. Here's a fork of ridem's Shopify gem, updated for a modern install of Ruby.
NB: The script always keep in sync Shopify's accepts_marketing field with Sendy's unsubscribed field. I added custom fields like country and order count as an example of what we can do with it.
First make sure that you have Ruby installed with the following gems:
activerecord
, protected_attributes_continued
, shopify_api
, yaml
, mysql2