At first, the mouseover told me a little info:
Then, clicking the icon gave me more detail:
BAD SECTORS? Oh no! I clicked the message to find out more. It apparently brings up a utility called “Palimpest Disk Utility”:
In addition to showing the drives in my system, it also allows me to test the drives via GUI tools:
I don’t remember the last time I was happy to see a failing hard drive! Maybe this tool will make it cool to find a hard drive with bad sectors.