I've had Activity Monitor running in the dock of my PowerBook as long as I've owned it. While it seems to me that iCPU doesn't do anything more than Activity Monitor can do (actually, even less, as Activity Monitor's dock icon shows CPU, system memory, and disk activity), it looks good. Heck, it's Freeware too.

I'm looking forward to the author addressing the relaunching issue and perhaps offering a few more icons from which to choose.