This is a Nagios/Icinga compatible check plugin for PoE capable Switches that implement POWER-ETHERNET-MIB. It queries a switch with SNMP and produces warnings if these values exceed a given threshold (either set in the switch itself or via command arguments).

copy check_poe_consumption_snmp.sh to your Nagios/Icinga plugin directory (usually /usr/lib64/nagios/plugins/ )
Edit your Nagios/Icinga config accordingly.
For Icinga2 you can copy check_poe_consumption_snmp.conf to your CheckCommand-Definitions (usually /usr/share/icinga2/include/plugins-contrib.d/ )
If you are running icinweb2-module-graphite you can place the provided check_poe_consumption_snmp.ini into the template directory (usually /usr/share/icingaweb2/modules/graphite/templates/ or /etc/icingaweb2/modules/graphite/templates/ )

Usage: check_poe_consumption_snmp.sh -H <FQDN or IP> [-C <SNMP-Community>] [-v <snmp_version>] [-w <warning>] [-c <critical>]
 -H <FQDN or IP>        FQDN or IP-Address for SNMP Query (REQUIRED)
 -C <SNMP-Community>    SNMP Community string (OPTIONAL, default: "public")
 -v <snmp_version>      SNMP-Version (OPTIONAL, default: "2c", also currently only 2c is supported)
 -w <warning>           Warning threshold (in %) for watt consumption (OPTIONAL, default: threshold found in SNMP, 50% if no threshold is found)
 -c <critical>          Critical threshold (in %) for watt consumption (OPTIONAL, default: threshold found in SNMP, 80% if no threshold is found)
 -h                     Displays this help message

onkelbeh for initial idea