I would recommend you look at the already-existing "Splunk for *Nix" and "Splunk for Windows" apps, both of which do this already for common operating systems.
If by some incredible misfortune these do not support the system you are trying to collect from, they would still be good jumping-off points for learning how to support the same thing for your own systems.
Also, both of these are "Splunk Supported" meaning that if you have Enterprise support you can submit enhancement requests against them and be able to get Splunk themselves to work on improvements. http://splunk-base.splunk.com/answers/4844/how-can-i-submit-an-enhancement-request
found this answer, and it got me part way to what i wanted. I installed splunk-app-for-unix on my indexer and splunk-add-on-for-unix on each of my two universal fowarders. those forwarders have been working (sending other application data) for some time. however, after installing what i expected to be this OS status app, the splunk app for unix windows shows data for the indexer only. the other two hosts don't appear. regular search shows that pertinent data are coming across, so what have misconfigured? haven't found a button in the app-for-unix to tell it use other hosts' data.