Update: This project is no longer maintained.
Demo: https://apex.oracle.com/pls/apex/f?p=16371
Source: https://github.com/vincentmorneau/oracle-rwd-email-template-api
Update:
1.1.0
* Templates are now parameterized
* More code refactoring
1.0.0
* Decoupled the API from the send mail feature. Now returns a CLOB value.