How to watch a SQL Server transaction log?

Question

I need to watch the SQL Server transaction log and execute some actions when specific changes happen.

Is this possible?

Using regular database triggers is not an option at the moment.

EDIT: The need is to watch table data changes, not structure. So when some table gets insert, update or delete, some action must be done. The reason behind using transaction log is to easily add some functionality to a database without changing its structure.