I found the answer to the problem.
I had to add another plugin element for the measurement.
So, I added the following to the server definition and it worked fine.
<plugin type="measurement"
class="org.hyperic.hq.product.SigarMeasurementPlugin"/>
The only problem I seem to be left with is, when I use the DaemonDetector, I can not seem to be able to delete the resources. I shut down the agent, remove the plugin.xml, restart the agent, delete the resources from the Server console, and they come right back in the dashboard, to be added to the inventory.