There's also smartctl, by the same developer as 7zX.

Most of the drives that ever failed on my machine never reported a bad S.M.A.R.T. status. They just dropped blocks left and right until they died a silent death.

I've come to the conviction that S.M.A.R.T. itself seems to be pretty useless.

Would be great if there was Growl integration!

Onyx, like Disk Utility, only checks SMART status when started. SMARTReporter checks at regular interval without needing user intervention.
Thumbs up to developer for this nice open-source app.

Sweet. I've taken my copy down now. :)

SMARTReporter's webpage is working again.

If you cannot download SMARTReporter, use OnyX.
Among all the functions that OnyX is able to do, there's also this same function performed by SMARTReporter.
You can find OnyX here:
http://osx.iusethis.com/app/onyx

Ok, since this guy's .Mac site went down and since there doesn't seem to be any other place to download it, I've decided to temporarily put the app up at this location:
http://kumaran.vijayan.googlepages.com/SMARTReporter.zip

Note that is a download for the slightly older 2.2.0 version. The current version is apparently 2.2.1.

Holy crap, the guy's .Mac site went down. You can't download the software now... Does anybody know what happened?

This takes up no processor cycles, no room, it doesn't even need to take a space on your menu bar, it can operate in the background. And It May Just Save Your A**. It saved mine.