I'm a big fan of self-analytics. I also like small-but-useful command-line tools of this nature. This is pleasantly documented and purpose-driven.
If you're looking for something more focused on short daily summaries of what you've done, I wrote a similar tool called wj:
It's more about organization and presentation than privacy. For example, it can generate a tex file that converts your entries into a nicely formatted pdf file.
I also like the automated self-analytics Stephen Wolfram uses:
http://blog.stephenwolfram.com/2012/03/the-personal-analytic...