I'm hopeful that because it's lightweight and written in C the program itself won't consume many of the Raspberry Pi's resources. If you wanted, you could probably run the program as a service when the machine starts and not notice any difference. The CPU data is sent from a minimal Web API, which is built into the webserver. It sends out the CPU percentages as an array in JSON format. This means that most of the work is done by the browser (all the plotting and scrolling) and on the server side we just need to send an array of numbers every second or so. And whilst I was at it, I also included the ability to monitor the core temperature (if it is running on a Raspberry Pi).
I have put the resulting project on GitHub, so if anybody wants to have the ability to monitor their CPU cores over their network they can try it. I expect it will work on other Linux machines too, it's not restricted to the Raspberry Pi. The number of graphs is dynamically updated, depending on the number of cores you have.
This is how it looks (in this case showing the graphs on a simulated iPhone 4s):
If you want to, you can try it out like this:
git clone https://github.com/davidsblog/rCPU
sudo ./rcpu 80
...which will only work if you're not running an existing webserver on the machine, otherwise substitute the 80 on the last line for a different port. When the server is running, simply point a browser at your machines IP address (and port if its different than 80) and enjoy.
I did notice that the graphs don't plot very nicely on the default browser included with Raspbian (although if you install an alternative like Chromium it should be OK). But since the purpose is to monitor the CPUs remotely this should not really be an issue.
The little LCD TV I tested the Raspberry Pi with wasn't very good, so I wondered if it was possible to remote into the Raspberry Pi from another machine. I found that this is no problem when I looked here. So I tried the following commands:
sudo apt-get install tightvncserver
...on the Raspberry Pi and it worked perfectly. Then with a copy of the TightVNC client running on my windows machine, I can access the Raspberry Pi remotely. This is awesome.
I used that approach to do more testing of my simple C# webserver, so here I am testing the webserver in TightVNC ... and also checking that the page is being served over my network to the PC in internet explorer:
...and finally, here is the Raspberry Pi serving the same test page to my iPhone:
OK, that all seems to work. I've just got to figure out what to do next now.