I have installed i8kutils and thought that I could use these conveniently. I thought I would find some config file to set temperatures. I haven't found one, and running "i8kmon -d -a -t 5 &" doesn't seem to work.
I did a google search with the terms "gnome linux cpu temperature applet" and got a lot of hits. The link http://blog.taragana.com/index.php/archive/lm_sensors-guide-or-how-to-monito... was very helpful on what to install to get sensor readings.