Interesting! I just had a quick look at the video and was looking at request params. Does martini support optional params? For example:

  m.Get("/something/:optional?"...

Something like Laravel's request parameters: http://laravel.com/docs/routing#route-parameters

or even route filters. Those would be suitable for that Auth demo, it looks like a filter, but would also be nice to have a group for routes and filter over those.