Munin Aggregate Graphs from several servers

There is a way look:

[ppke.hu;All_Totals]
  update no
  uptime.graph_title Uptimes
  uptime.graph_vlabel uptime in days
  uptime.draw LINE2
  uptime.graph_order \
    host1=host1.ppke.hu:uptime.uptime \
    host2=host2.ppke.hu:uptime.uptime \
    host3=host3.ppke.hu:uptime.uptime \
  uptime.graph_category system

I think you get the idea.

Later I replaced my munin monitoring with a more complete solution....

Yes, you can build aggregate graphs.

Here's the how-to on the Munin site.

Basically, you create a fake node in your munin.conf, and the describe the sources, but it's easier to read the link than explain.