I've just completed a prototype for a system monitor made with an arduino uno, c#/.net.
At this moment it sends CPU% and Network Load, but I want to add RAM usage and DISK Usage.
I've already added those to the software, just need to order new parts for a new prototype.
Network load is detailed by a serie of leds and a servo which operates for 10/100/1000Mbit.
If you're interested in more details , check out https://www.bartjanssen.be