I didn't know that you can build snippets for iTerms's toolbelt. Now I know. And I built a small but wholesome system monitor which I was always missing as a sysop-dude:

- CPU/memory usage - network traffic - open ports - file system moitor - folder size watch dogs for common cache/log/temp folders

Each monitor lists the usage per process/app/service, it allows filtering and offers a lot of more details like PID, running user, etc.pp.

You can pause the whole thing or each of the sections to not overload the system with unnecessary "pollings".