Note : This functionality only applies to the High Availability Service subscribers

Under the "Alert Contacts" menu option, add your phone number, including country code to the phone number list.

e.g. for USA and Canada:

Phone number +1 123-123-1234 enter this:

11231231234

for UK:

+44 123-123-1234 enter this:

441231231234

Next configure a new rule to send you a text alert. 

eg: