check_sa (Visit this link)

check_sa is a Nagios plugin to check the status of one or more performance counters monitored through sa and sar in the Linux sysstat package. It supports simultaneous checking of multiple counters, filtering by included or excluded device, and shell-style globbing for counter and device names. I think the code is also pretty readable if you want to hack it; I'd love for someone to help make the parsing part a little bit faster.

It relies on the sadf utility and may or may not work on other platforms -- if anyone would like to contribute fixes to make it work on Solaris, BSD or any other Unix-like, I'd love to have them.