The invasion of privacy is the obvious problem. But it isn't going to be functionally very useful to me either.
You're going to capture hours of walking and/or seemingly doing nothing, exchanging pleasantries/small-talk/banter. Without access to my thoughts, this is stuck in some superficial layer -- useless other than to maybe surface a reminder of something trivial that I forgot (and that's not worth it). Life happens in the brain, and you won't have access to that (yet).
You're going to capture hours of walking and/or seemingly doing nothing, exchanging pleasantries/small-talk/banter. Without access to my thoughts, this is stuck in some superficial layer -- useless other than to maybe surface a reminder of something trivial that I forgot (and that's not worth it). Life happens in the brain, and you won't have access to that (yet).