To be frank I would pursue either a more simple email action route due to the ability to easily customize the presentation of information which an SNMP trap forward will not allow.
Any ITSM tool is going to parse a certain amount of information but then push the remaining information into a human readable note or ticket description field that traps are not necessarily the best at.
That said the best integration would be API based on both SWIS and ServiceNOW web services - we are having some built between ServiceNOW and our other ITSM and it's been good so far.