It remains to be seen how useful such a log would be to a person, and if the privacy concerns can be sorted out. Until we build it, we won't know. People regularly take photos during vacations, for example, and arrange them into a neat history of the trip. I'm actively designing and building the Factoid device. The photo above is a non-functional mockup of what should be feasible.
Power consumption is a big issue.
This looks feasible, and could even be improved upon if I was willing to design a custom chip. Privacy is another big issue. There is a natural evolution for this device. The next step is to add different types of data to the log. Voice memos seem to be a popular choice, and would involve adding a microphone, and perhaps a button and a speaker.