Well Sonos devices have line inputs too. Anything connected to a line input can be played anywhere/everywhere. There's also an iPod dock accessory that streams wirelessly and also gives you control of the iPod via any smart phone/tablet/PC/Mac/Sonos Controller.
When I'm installing Sonos for clients I use the line inputs for stuff like the TV audio (Freeview/Sky) and a local CD player if required. But TBH, once all the music is stored centrally there's very little requirement for much more than a dock and Freeview/Sky audio, and on rare occasions a CD player. Do you need anything more than that?
Actually the Sonos WD100 iPod dock went end of life in November. Just before Christmas they released an update which allows you to play the library direct from an Apple device through the Sonos app. Much like Airplay but proprietary to Sonos.