Hi Marcus,
yes, it is a master - slave setup and it seems that would be the best way to do it. However, my slave Raspberries are not capable of running an OMD site, they are old Raspberry B with 256MB RAM. I tried and it literally brought the system to a halt. Also I would like to reduce complexity of the remote system as much as possible as I do not have access to all sites regularly.
Do you have a pointer to using the Nagios style checks? I have used Nagios in the past but not more than out of the box in a very simple setup…
Thanks,
Fabrizio