Dear jpade,
I understand what I did wrong now. But by now I tried to do some debugging myself, I tried:
And it showed me a different file then the one I edited. I'm guessing you pointed me to a more general file and "crontab -e" gives a user specific crontab file. I ended up thinking why not just use the GUI for "startup applications", press "add", browse to cgmon.tcl location, add description and some comment, and what do you know, works like a charm. Starts right after unity boots every time. I don't know the implications of me running like this, do you think your method better handles things?

I added:
So the wireless network adapter will have enough time to reconnect.