arbtt (hackage): arbtt is a background daemon that stores which windows are open, which one has the focus and how long since your last action (and possbly more sources later), and stores this. It is also a program that will, based on expressive rules you specify, derive what you were doing, and what for.  The documentation, which includes the changelog, can also be found at http://arbtt.nomeata.de/doc/users_guide/.  WARNING: The log file might contain very sensitive private data. Make sure you understand the consequences of a full-time logger and be careful with this data.
Keywords: desktop|gpl|program