I now have Nagios configured to submit passive checks w/o nsca since everything is on the same machine. Currently, snmptrapd will execute a specific script per OID.
traphandle .184.108.40.206.4.1.3220.127.116.11.18.104.22.168.22.214.171.124.126.96.36.199.188.8.131.52.184.108.40.206.220.127.116.11.0.1073748859 /usr/lib/nagios/plugins/eventhandlers/submit_check_result_w32time
submit_check_result_w32time looks like this:
get the current date/time in seconds since UNIX epoch
create the command line to add to the command file
cmdline="$datetime] PROCESS_SERVICE_CHECK_RESULT;$host;w32_time;1;\"W32Time Event\""
append the command to the end of the command file
$echocmd $cmdline >> $CommandFile
/var/log/nagios/rw/nagios.cmd contains this after snmptrapd matches the oid:
 PROCESS_SERVICE_CHECK_RESULT;fqhost.domain.com;w32_time;1;"W32Time Event"
That said, how do I get Nagios to check the command file? I don't have any of the check commands mentioned in other posts. Is there a common check command that I should used in the service definition, or are we left to write our own?