I wonder how I can log the screen status, at least on diablo. I've done some search and found that I could use dbus-monitor --system and look at the value of display_status_ind. So,
gives me more or less what I want, except the time, which is important information (I'd like to know exactly when the screen is on or dimmed, as I suspect this can be the cause of my battery drain problem). To get the time, I can add the --profile option (the time is on the second column, as the number of seconds since the epoch), but I no longer get the display_status_ind value!

I could write a script that filters the dbus-monitor output (hoping there's no buffering problem) to get both the display_status_ind value and the time, but is there any better way?

Note: Ctrl-C does not work with dbus-monitor. Ctrl-\ is OK, but generates a core dump (if enabled), as usual. So, I suppose that the best way to terminate it is Ctrl-Z (fortunately, it isn't blocked) and "kill %1".