Its actually pretty simple to do MRTG statistics on this.
http://www.swerts-knudsen.dk/mrtg/First determine where you want MRTG to create the stats. I have a mrtg ibay and a sub-folder called hw. Create mrtg .cfg file with the following for 2 disks.
workdir: /home/e-smith/files/ibays/mrtg/html/hw
Target[temp1]: hddtemp -n /dev/hda&hddtemp -n /dev/hda
MaxBytes[temp1]: 200
Options[temp1]: gauge,nopercent
Title[temp1]: Disk hda Temperature
PageTop[temp1]: <H1> Disk hda Temperature</H1>
WithPeak[temp1]: dwmy
YLegend[temp1]: Temperature
ShortLegend[temp1]: Celcius
LegendI[temp1]: Temp:
LegendO[temp1]:
Target[temp2]: hddtemp -n /dev/hda&hddtemp -n /dev/hda
MaxBytes[temp2]: 200
Options[temp2]: gauge,nopercent
Title[temp2]: Disk hdb Temperature
PageTop[temp2]: <H1> Disk hdb Temperature</H1>
WithPeak[temp2]: dwmy
YLegend[temp2]: Temperature
ShortLegend[temp2]: Celcius
LegendI[temp2]: Temp:
LegendO[temp2]: