I've been looking at SNMP a bit more closely recently. One thing that has struck me is that while there are a number of java based SNMP clients, none of them seemed to be complete, and I couldn't obviously find one that could produce charts easily.
This is easy, right. So a little while later snmpgui was written.
OK, so this is version 0.01. I've been able to retrieve a list of things to monitor (that's the long list of OIDs above). Clearly that needs prettifying a bit - a tree view would be a nice next step. And I can retrieve values and produce pretty charts. That's incoming bytes on my main network interface.
It's a simple proof of concept - but it proves that something can be done pretty easily, and that it works.