Hi,
It has ability to send email when threshold changes.
i think u have not created a New integration task in u r metric maintenance package.
try this steps may be it will help you..
1) Go to Your metric maintenance package depend on u r scorecard.
2)At top u will see between New job and New url , u will see New Data integration task
3) Click on that and select new metric maintenance.
4) select u r metric package.
5)It will ask for Name, Type: - Email Alert Notification ,click next
6)under metric data options - select: recalculated derived values.
and under Additional Options : select emails from watch list.
7) select option: save only.

click finish.
May be it will work for you...