I have worked a lot with the Hyperic Database and writing Custom reports via Jasper Studio (newest iReports version).
It is not a easy task and took a lot to understand the relationships within the tables since there is limited documentation. Additionally, I did most of my development in version 4.6 of Hyperic, when I recently upgraded, the the measurement table's DSN column (which is how you get the individual metric name) is now Encrypted, though during our upgrade I disable the encryption of those values so that my reports would continue to function.