You'll probably end up using Munin. It allows for single node or multi-node monitoring of various metrics. It looks a bit daunting to get it set up (it really isn't) because of the command-line configurations. The most difficult part of it is getting permissions correct.
In any case, following is the Munin plug-in that I wrote (to run on the RPi) to monitor temperature:
case $1 in
graph_title RPi Temperature
echo -n "temp.value "
/opt/vc/bin/vcgencmd measure_temp|cut -d'=' -f2|cut -d\' -f1
That's all there is to it. All but the last line is Munin-config related. The last is the command line to pull in the temperature.
One slight change to your requirements, I believe that Munin gathers metrics every 5 minutes.