It works with the iPad, but I can't answer whether it works with Sonos.

In any case, music and videos can be streamed simultaneously to 5 devices, which should also work with Sonos. It can certainly be used as an iTunes library.

I cannot answer this question conclusively because I do not use it for this purpose. But the way it works is the same as with an external hard drive. If it works with one, it should also work with this one.