I did a similar experiment in about 2005 using a small iRiver iFP [1] and reached the same conclusion.
It needed a physical "Something interesting just happened" button that could be annotated later. At the time, creating custom hardware as well as the entire software/service stack was more than I was willing to bite off.
The iFP is tiny, roughly a 4" long by 1.5-2" cylinder. It easily covered a full day, the silence detection worked great, and quality was fine when used in a pocket or on a belt. Basically, the stuff that I expected to be difficult was already solved.
It needed a physical "Something interesting just happened" button that could be annotated later. At the time, creating custom hardware as well as the entire software/service stack was more than I was willing to bite off.
The iFP is tiny, roughly a 4" long by 1.5-2" cylinder. It easily covered a full day, the silence detection worked great, and quality was fine when used in a pocket or on a belt. Basically, the stuff that I expected to be difficult was already solved.
[1]: https://en.wikipedia.org/wiki/IRiver_iFP_series, https://www.cnet.com/reviews/iriver-ifp-790-digital-player-r...