Defining a Device Group Specific URL

Hi there,

We'd like to look at alternate ways of implementing device detection, rather than using the link alternate tags.  I've found that there is the option to define Device Group specific URLs, but the documentation is limited:

http://docs.adobe.com/docs/en/cq/current/developing/mobile.html#Defining a Device Group Specific URL

Can anyone describe exactly what this option does.  And/or an example of how to use it?

Thanks in advance for any pointers!