It is not an icon, but a stack of system monitors. Here is the link to the Web site:
http://members.dslextreme.com/users/...m/gkrellm.html
To install it:
#apt-get install gkrellm
Then I looked for plug-ins:
#apt-cache search gkrellm
That provides a list of plug-ins in addition to the ones provided. After you finish, look under applications > Debian > apps > system and it will be in that menu. Click on it to run it, and then right click on the panel anywhere to configure it.
Good Luck. Let me know how it goes.