Adding a CPU monitor widget in the top corner like in Gnome2

I wonder if you can add a widget or something like it in the top corner (next to volume and WiFi and things like that) that displays current use of CPU and maybe RAM. I know you could add stuff like that in Gnome2, altough I can't find a feature like that in Unity or Gnome3.


For Gnome Shell: http://www.webupd8.org/2011/10/gnome-shell-system-monitor-extension.html

For Unity: What can replace system monitoring in the top Gnome Panel in Unity?