Thinking of mobile usability, and being able to stream to Volumio (as well as using local phone music in the Volumio playlist), I think a mobile webpage only wont suffice.
A mobile webpage is enough for remote control, as well as playing from other sources, but if you want to stream from your phone to Volumio you will need 3rd party apps like BubbleUPnP.
A while ago I worked on a dedicated Volumio app (using the MPD protocol) with the support for streaming directly from your phone. Unfortunately I never came to the point of implementing UPnP (or any other streaming method) and ended up with just a MPD client, Volumio style.
Would it be a good idea to have a dedicated app (like Sonos) from which you can control your Volumio in addition to the WebUI? This would also allow us to have notifications on our phone, playback control from your lockscreen, volume control while receiving calls (as suggested on the forums) and much more. With the new system (and abstraction layers) we are no longer limited to the MPD protocol and create a solid connection between the phone and Volumio, making a lot of things easier like the Album Art and having a settings menu. Ofcourse the UI would and should match the new WebUI.
Let me know what you think.
Some pics of the app I worked on.
I’m currently on a Nexus 4, but used the older Samsung to check backwards compatability and UI scaling. To get to the browse/playback/playlist tab you can just swipe left and right.