What services do you have in mind?
There is a plugin that may help: http://support.rhq-project.org/display/RHQ/Plugins+-+Plugin+-+Network+Services
Otherwise, checkout my "How to write a plugin" whitepaper that describes such a service: http://www.redhat.com/f/pdf/Write_A_Plugin_WP_web.pdf
I'm pretty sure the NetworkServices plugin is what you want.
that's the descriptor for that plugin - it shows you the resources/metrics it supports.