Alert on changes to Property Values

Use a script datasource, get the data out of the device property with the 
usual hostProperties groovy line like:

firmware_vers = hostProps.get("auto.entphysical.firmwarerev") 

Remove any NaN characters or create something like a hash sum and convert it to an integer so LogicMonitor can store it in a datapoint.
Then use the one of the numerous delta functions as a threshold:

Does not sound particularly difficult to me.