There seems to have been some giant leaps in this recently and now are almost affordable to me. I'm looking to do something fairly basic, or perhaps complex depending on how it works out. I would like to control 3 - 4 audio zones with an iPad or android phone to play pandora or control a music library. I don't mind if all zones have to play the same thing, but they must have independent volume controls. Ideally, I would like to have some basic commands controlled by voice recognition. Simple stereo on and open the garage door or something.
It looks like Control4 will suite some of my needs, but the voice command aspect isn't there... with any product I have found so far. I'm competent in wiring and computers so combining several systems is acceptable.
If you're fine with using your phone or a tablet that's the way to go. But it does help to have a few purpose-built controllers installed on the walls or in a place where they won't get moved. As in, when your phone isn't handy, is in-use or the battery is dead. No need to fumble around to find a tablet that's been shaghai'd for something else.
If you're OK with the price-point, it's hard to beat the ease of use with a Control4 setup. Very spouse-friendly.
But for just audio (pandora, amazon, local mp3s, etc) then consider a Sonos setup. You can have as many Sonos output devices as you'd want rooms with audio. Either ones with their own speakers built-in, with their own amp and separate speakers or without an amp using your own setup. The upside is their controller software works on just about any kind of smartphone or tablet (in addition to their own remotes). We've had one plugged into our Russound whole house setup for years and it's been great as an additional source (along with mp3, CD jukebox, radio, satellite, etc).