Incidentally, I just complained in another post about the way that needing to "invoke" voice mode makes it much less fluent. You may at least want to pop that one on to the mental back burner to see if there's a solution you can think of for it. I don't know what, but something that makes the friction of invoking a voice app less would help a lot. (I assume this is where Amazon Echo idea comes from.)
1. A number of early customers we've spoken with don't like the idea of an always listening device. The perception is an invasion of privacy.
2. There's a fear that someone outside the home could simply yell a command like "unlock the doors" to gain access. There are a number of ways one could solve this, but it's a fear we've heard about.
So the extra friction of taking out your phone and pressing a button so far seems worth the added layer of privacy and security, but we're definitely thinking hard about this one.