I have successfully used http://autoaudit.codeplex.com/ for triggers and I've been happy. The particular system I used it in wasn't what I would call a high volume OLTP environment, since the tables we managed were control tables for a dimensional data warehouse - so the majority of the big data was managed with a different paradigm. However, I certainly would recommend it and expect to use it in future products and am even looking for similar system for a more-OLTP-based Oracle project I'm working on now.