Extensions to System Monitoring Plugins

I'm interested to see if anyone has done any extensions to the Oracle-provided System Monitoring plug ins, or perhaps developed their own.

I've extended the SQL Server plug in and added several jobs to it, so I can centralize my database management in the Grid Control Console.

Some of the custom jobs I've created include:

1) Backup User Databases

2) Backup System Databases

3) Backup Transaction Log

4) Shrink Transaction Log

And I'm going to add a few more - most likely object reorganization, and then I'd like to add some metrics to collect metadata about the databases I have installed - tables, indexes, other such objects.