Hi Michael,
You issue is triggers are based on incident events. So there is no way that I know of that can fire a trigger when the SLA is not met.
But another way to achieve the same results would be to use reports and then use Action Schedule to do what you want.
First create the report to get the results you want and then save it:
Click on 'Schedule & Queue' and then select 'Action Schedule'. Select what action you want to happen and then how often you want it to run. In the example below I adding my self to the Watchlisted and then let it notify me.
I scheduled this action to run every hour. Note you may want to change your report to exclude any results you have already changed. In my example I added my self to the Watchlisted. So in my original report I could of added, where my name was not on the Watchlisted. This would ensure I'm only getting notified about new items.
I hope this helps.
Regards
Mat
