Are there any notifications mechanisms for KDE and/or GNOME which read their data from
You can use SmartMontools to control and monitor the SMART features of yours disks. I think it comes with most of the common distros.
[Edit: There's also GSmartControl, which is a GUI front end for SmartMonTools and claims to "automatically reports and highlights any anomalies". Haven't used it personally though. Is that the kind of thing you are after?]