Excellent job, Tom. I don't think having the slave speaker wired is a deal breaker. But, for those who absolutely need the slave wireless, there is still the issue of L/R. I don't think iTunes software is setup for it. What if the master Airplay speaker had WiFi, AND Bluetooth connectivity? You could have a small add-on amplified bluetooth receiver for the slave speaker. (And have that nifty bolt I was talking about.)

Epic 80/600 + M3's + M3 Algonquins + M2 Computer + EP125
I think I'm developing an addiction.