Wow, it seems like this will take a while to come out and I didn't see any word on pricing.
A good alternative to this is a Beep. Beep sells devices that plug into any speakers audio jack to let you stream music from your phone. What's better is that it also syncs up multiple units so you can have your music in sync across your house.
I don't think it's been officially announced yet, but at least one of the reports on the new Google Cast stuff, and a dev who claims to work on one of the partner apps commenting on reddit, suggest that the audio cast stuff will synced audio across multiple devices.
A good alternative to this is a Beep. Beep sells devices that plug into any speakers audio jack to let you stream music from your phone. What's better is that it also syncs up multiple units so you can have your music in sync across your house.
We've used them in our office a few times and love them. https://www.thisisbeep.com