Optimum7 has finalized a custom API Integration between Jet.com and Shopify that enables store owners to list their "selected" products on Jet.com. More details can be found here. http://www.optimum7.com/custom-programming#jet-api-integration
This is not an automated DIY tool yet but we plan on launching this as a web based DIY tool similar to Amazon.com listings UI on February 2015.
We have developed application which manage the product/inventory orders on jet.com automatic order acknoledgement etc.
and now we are developing for shopify to sync with jet.com
mail me for more requirement and feature
Our current solution can provide you to manage products and orders informtions in csv/xlsx format from single application.
We can also help you to convert/fetch/pull data from/to shopify and jet.com
We are also working on amazon.com ,ebay.com, and other marketplaces
We can provide you custome soluton as per your need to manage all processes from single application/dashbord.
Please send us more details about your products, orders frequency, and your budget for solution.