What do you consider a managed node? A Nimsoft Robot? a device monitored with rsp? A Network device monitored with SNMP? A virtual machine?
Robot couting is easy you can see the number in the botom right corner of the robots windown in infrastructure manager when you select a hub. You can also look in the CM_COMPUTER_SYSTEMS table in your NiS database to see a more complete list including discovered devices.
there is also the billing and usage metering probes which can generate reports on what is monitored.
Retrieving data ...