When devices that supported AirPlay started showing up at CES this year it left Sonos at a bit of a disadvantage. Airplay requires special hardware for it to be supported in a consumer device and the Sonos devices didn't have that chip. But that's not the end of the story.
The engineers at Sonos put their heads together to find a way to make AirPlay work on Sonos devices like the S5 which we looked and loved at last year. It's a bit of software and a bit of hardware. But if you have an Apple AirPort the you have all the hardware you need.
To make AirPlay work on the Sonos, you connect an AirPort Express directly to your Sonos S5, both the Ethernet and audio cable. Once connected and configured properly, when you play something on the AirPort via AirPlay, the Sonos will pick it up and switch to play the audio from that device automatically. Boom, instant AirPlay.
Ok, it's a bit of a kludge, but damn, it works great.