This is very useful for creating URL aliases, and managing redirections from an old URL to a new one. A very similar extension has been added into Joomla since 1.6 version (Redirect component), but ReDJ supports powerful regular expressions that allow to match more than one source URL.
In this way it is possible to create a group of redirections with just one ReDJ item. It's so easy.
Also, now ReDJ comes with support for macros into destination URL. This means that from now the destination URL can be dynamic.