SSD-LED is a freeware activity indication application.
Here are some screenshots to illustrate the features and user interface of this application:
Neat system tray app to constantly check on HDD. Screenshot of SSD-LED - 758px · 531pxThe tray LED indicator is the star of the show. Screenshot of SSD-LED - 1550px · 1325pxThe associated graph is cool and informative as well. Screenshot of SSD-LED - 1550px · 1325px