I would like to know how much bandwidth is being used on my server. Not HTTP bandwidth, but all protocols. Basically iftop data over time continuously logged. Then I could write a simple python script to process it and provide aggregate info.
instead of writing it all new,
you could use tools like cacti.
With it you can analyze your network.
I use ntop for things like this. There are a few ways you can store and generate reports with it.