I have created a workflow for the Workflow iOS app that will use the Subsonic API to collect the current Now Playing item and allow you to share it via Twitter, Facebook and Instagram.
THIS WORKFLOW USES THE SUBSONIC API WHICH REQUIRES A SUBSONIC PREMIUM LICENSE.
This workflows pulls the items marked as "Now Playing" for a specified user on a specified Subsonic server. It uses the Subsonic API to find the title, artist, album, release year and cover artwork for the "Now Playing" item and then allows sharing on Twitter, Facebook and Instagram.
The workflow also has error checking in case the Text configuration action is not setup properly. It will confirm the title and artist in case there are multiple players being used by the user at the same time.
More information, and links to all versions can be found here: http://workflow-vcs.de/history/Share%20Now%20Playing%20From%20Subsonic%20%28v5%29
Enjoy!
Neil Forker