I have recently started to look into the Google Chromecast Audio and the ability to use the device with LMS. Luckily, a user over on the slimdevices forum has solved this problem. Check out CastBridge as seen here: http://forums.slimdevices.com/showthread.php?104614-Announce-CastBridge-integrate-Chromecast-players-with-LMS-(squeeze2cast)
As of now, multiroom sync is not working (this is now supported within the CCA firmware), but the author philippe_44 is working on it. I hope he makes this happen, as this would allow for a very cheap replacement of the squeezebox hardware. You can purchase two Chromecast Audio’s for $55 over at the main Google site: https://store.google.com/product/chromecast_audio
Happy Listening!