[ Thanks to kiterunner for this link.
]
“Busyhot is a nice little Gnome panel applet for
showing real time CPU load time and temperature from click of a
mouse in your desktop.* The default display inside the panel shows the total load for
all processor cores and the min-max range of core temperatures.
* And as you can probably infer from the screenshot above, a mouse
click on the panel brings up a small window which shows the
detailed loadings and temperatures of all processor cores.”