Email Notification To DBA When Threshold Of 80% Reached For Archive Log?

 11.2.0.3 I want the database to email me when the threshold of 80% is reached for the archivelog and backup piece at recovery_dest folder how to do this. Is this the dict table  I will check for threshold? 

select * from v$recovery_area_usage;

 FILE_TYPE            PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES -------------------- ------------------ ------------------------- --------------- CONTROL FILE                          0 0               0 REDO LOG                              0 0               0 ARCHIVED LOG                       2.02 1.06              21 BACKUP PIECE                       4.76 0              11 IMAGE COPY                            0 0               0 FLASHBACK LOG                         0 0               0 FOREIGN ARCHIVED LOG                  0 0               0  7 rows selected.