This looks like a privacy nightmare, even for the wearer - aren't going going to have to continuously ask for permission for every single person that you're in recording distance of when not in a public space?
That depends on where you live. In some European countries for example it's perfectly legal to record for personal purposes without announcing it. Bear in mind the phrase "for personal purposes" is doing a lot of heavy lifting here, for example it's common that you can't use the recording in court if you haven't announced you're recording and since that would no longer be personal use.