We're not able to 100% confirm this, but it's our understanding that Langify has the ability to translate custom options built into its app. Here's a response we received from one of our users:
Langify confirmed with me this morning: The Shopify options will be translatable via the "Translations / Products" section in Langify, whereas the app options must be translated in the "Translations / Custom" section in Langify.
If you do use Langify, please let us know so we can get more details on their compatibility, and improve it as needed :).
If you're interested in more tools to sell internationally or translate your store, we have a couple of articles on our blog that may be helpful: