I use syslog alerting for this. I just look for a particular Message Type Pattern (e.g ENVMON*) and alert on it accordingly.
In our environment we defined a Universal Device Poller that we call Cisco Temperature. This takes the value from the specific OID (ciscoEnvMonTemperatureStatusValue) and transforms the results into TempFahrenheit value for our Cisco devices. We then setup an alert using "Custom Node Poller" and trigger when value greater or equal to 88 from any device . I can provide more specifics if you still need help setting this up.