I looked at the API docs for Somfy, and some other sources, and it's definitely possible to write a plugin for them. Without a dedicated plugin, it could be done using the Cynical Network plugin and a TCP Out device. And a TCP In for status. It's JSON formatted strings sent via socket writes to a specific port on the device's IP address.
I don't have any of these devices, so I'm not particularly motivated to write a plugin. But if there's enough demand I might consider it.
Some discussion here:
https://community.smartthings.com/t/somfy-mylink/81197