I am also looking at Phase Alarms now. I think they might be a good solution, and would not need the custom module you suggested. They become active when the failure monitor is triggered, which is essentially when the phase goes to Hold. I found some options in BOL which I cannot find in DeltaV:

The following additional properties, which control the behavior of phase alarms in the unit module, are configured in the unit phase table for each phase:
Enable failure alarms on this unit phase - Is a Boolean property. If False, then the values of the other alarm-related properties do not matter. Defaults to True.
Phase alarm name - Is the name that will appear in the alarm details field in the alarm banner when this unit phase has a failure. Must pass the standard parameter name checks (characters, length, no name space collisions, and so on). Defaults to the unit phase name. If the phase class name is changed, the phase alarm name does not change. It remains the same as the original unit phase name.

Does anyone know where these could be set? Also, how to manage the fact that I would want the alarm to be automatically acknowledged when the operator restarts from Hold? I would not want the operator to have to do 2 things: restart and acknowledge.