Install MRTG if you haven't already got it. You can find RPM's out there if you're running an RPM friendly distro or take a look at the MRTG site here.
You will also need lm_sensors installed and working as described somewhere on these forums (sorry I can't remember where).
Add the following section to your mrtg config file.
###
# CPU Temperature monitoring
###
Target[cputemp]: `cputemp-mrtg`
Step[cputemp]: 240
Options[cputemp]: nopercent,growright,nobanner,transparent,gauge
MaxBytes[cputemp]: 125
Unscaled[cputemp]: ym
Title[cputemp]: cputemp
PageTop[cputemp]:<H1>Bayleaf CPU Temperatures</H1>
ShortLegend[cputemp]:&
YLegend[cputemp]:Temp Celsius
Legend1[cputemp]:Temp of CPU 1
Legend2[cputemp]:Temp of CPU 2
Legend3[cputemp]:
Legend4[cputemp]:
LegendI[cputemp]:CPU 1
LegendO[cputemp]:CPU 2
Next put this perl script somewhere in the executable path (/usr/bin, usr/local/bin....etc) and call it cputemp-mrtg. Make it executable etc.
#! /usr/bin/perl
$cputemp = `sensors|grep -o "+.*C.*(" | grep -o "+[0-9]*.[0-9]"`;
$cputemp =~ s/^M//g;
$cputemp =~ s/\n/\-/g;
$cputemp =~ s/\+//g;
($cpu1,$cpu2,$board) = split("-",$cputemp);
$cpu1 = int($cpu1);
$cpu2 = int($cpu2);
$board = int($board);
print "$cpu1\n";
print "$cpu2\n";
print "$board\n";
print "Sensor Data \n";
Fire up MRTG and take a look at the results (you may have to wait some time for anything meaningful).
If I could work out how to put images in this post I'd show you what my graphs look like but I can't so pity my stupidity
Hope that helps/interests/amuses someone.