with gnome-fallback and classic gnome shell, we had gnome applets available, but not in Unity. There was a system monitoring applet there that I could see may CPU and network bandwith used. I'm pretty sure that I can not have the same applets in Unity, at least not yet, from Can I use GNOME applets in Unity?. But how can I have such functionality with unity that shows me my system status in the upper panel? Or how can I create such thing?

Edit: One possible way might be to create a program to monitor network and changing icon in notification area is one way in order to show status.