David,
Best approach here is to enable ONLY the HSRP state change traps on the router. We do have the events and alarms mapped for HSRP state change traps.
Other way is to have an attribute on the router model in Oneclick which will report various states of HSRP like BGPPeerstate attribute and then configure a watch in Oneclick on this HSRP state change attribute .
We might also need to compile the MIb which has this state change attribute value incase you don't have it out of the box.