My example of DRBD Status Monitoring :

/etc/zabbix/zabbix_agentd.conf:
...
UserParameter=custom.vfs.drbd.status,sed '1,/.*/d;/^$/d' /proc/drbd | egrep -vc '(UpToDate/UpToDate|ns:.+nr:.+dw:.+dr:.+)'

+ attached xml file for the template to be import

feedback...