Simple monitoring tool with notification system

For some time now i need a software package or script selection that monitors my few servers for load spikes, disk usage, network traffic etc. and automatically sends an email (or xmpp) to notify me.

But the solutions i found need a master server or they are not much more than a framework that you need to configure for every sensor yourself.

I just want something simple and not centralised. Is there such a solution?

Edit: all servers Debian or debian based.