Hi Stefan,
The command-line workstation (CLW) is the most obvious choice, there is a large section on possible commands for it in the documentation, I think Config/Admin guide (get historical data options..)
There is a possibility to store metric data as flat files, configured directly in IntroscopeEnterpriseManager.properties, but it isn't a good option for performance reasons.
There is a JDBC API that can be used to get some data out of the EM as well but I think the CLW should cover most of any requirements.
Thanks,
David