Numerous languages are supported by the API (Perl, Java, etc).. I took a quick look in the 4.1 SDK that I have on my system and found "sis-status" as a call that returns quite a bit of information like blocks skipped, checkpoint progress, progress, state, etc.
As for seeing how busy a volume is, that sounds more like something you'd want to pull from DFM (different set of calls). If that's the case, there are different versions of DFM out obviously so some calls may be available in one version that arent in another. I looked in version 4 and found "volume-perf-status" which is described as "Current status of the volume based on performance events" but I'm not sure that will give you exactly what you're looking for..
HTH and good luck.
