Monitis-Mac-OS-scripts is a project mainly written in Shell, it's free.
Mac OS Monitoring Scripts for Monitis API
Example of recording load averages to Monitis using shell scripts os OS X
These are based on the original bash example scripts, but modified to focus on recording the load averages, and for the different xpath syntax in the default OS X installation of xpath.
monitis_create_load_monitor.sh
Creates the external monitor used to record the load averages. Don't forget to set the API key and secret in the script, or export the values in your shell.
$ export APIKEY="your API key"
$ export SECRETKEY="your API secret"
monitis_record_load.sh
Gets the load averages from the uptime command, and records them to the specified Monitis external monitor. The API key and secret are specified as command line arguments.
Examples
# create the monitor
$ ./monitis_create_load_monitor.sh
{"status":"ok","data":797}
# record the current load averages
$ ./monitis_record_load.sh -a <api_key> -s <api_secret> -i 797
{"status":"ok","data":null}