The ability to listen to the same songs as another phone at the same time. Have one queue for both phones that either could add to!
Updated on 2018-02-23
A similar idea has been posted here: https://community.spotify.com/t5/Live-Ideas/Real-Time-quot-Listen-With-quot-feature/idi-p/100613
Please add your comments/votes there and reach out here if you need any other help 🙂