Hi there Arjuna,

What exactly do you mean by "an event or a custom property being set"?

One thing you can have a look at is the EventBus where you can trigger actions to fire based on certain workflow events. The following blog by Joseph contains some good information on how he triggered notifications through the event bus. Your escallations might not be emails, but still I think it demonstrates the theory really well.

http://k2underground.com/blogs/fromthebench/archive/2008/02/13/custom-notifications.aspx

Regards,