I think it's worth mentioning that this is yet another fairly cool project that relies on an always-on* microphone. I don't remember who said it, but there was a very nice quote on HN recently about the currency of freedom i.e. it's not something you should never spend, but you should be certain you're getting your money's worth. :I

*I realize you can turn it on and off, but it's not designed to be done easily.