While perusing the web a few weeks back, I came across SMARTReporter. SMARTReporter is a wicked cool software package that can be used to monitor hard drive SMART data under OS X, and it is 100% free (you should probably send a small donation to the author if you decide to use it). Now that I have SMARTReporter in my software arsenal, I have a tool to monitor SMART data on each of operating systems I support:
For Solaris, OpenBSD, FreeBSD and Linux, I use Smartmontools
For OS X, I use SMARTReporter
For Windows, I use Active SMART
All three package rock, and they have saved my bacon on more than one occassion!