Maxwell answer is right, but is missing the download a url for the script:
http://git.recluse.de/?p=users/bzed/nagios-plugins.git;a=blob_plain;f=plugins/check_smart
i also add this line below on line 109 of the script, to avoid a warning
if (!defined($number)) { $number = 0; }
For those without nagios, the script requires a util.pm lib. Debian users can get it from
nagios-plugins package and other users can grab it from here:
https://github.com/Elbandi/nagios-plugins/blob/master/plugins-scripts/utils.pm.in
the usage is simple:
./check_smart.pl -i scsi -d /dev/sda
but i agree with exquisitor comment, a way to graph all (or at least some important) smart values would be great
UPDATE: the script DO output other smart values, but only if you choose the ata interface (-i ata). As today all drivers (even ata/sata) are seem as scsi devices, this create confusion (and its probably a bug)
So i recommend for those with ata/sata drivers to edit the script and on line 209 replace the check from "ata" to "scsi"