Currently most detail guide focus on creating mobile website with sub-domain like m.website.com for mobile site and website.com or www.website.com as desktop site cause is easier to cache by domain but also include apache rewrite and I can't nginx mobile guide for drupal. I hope to this discussion can come out some possible solutions to use nginx and write guide to setup mobile site.
Basic goal is using nginx automatic redirection mobile & desktop user to respective theme/domain with their device accessing with. Next is having a BLOCK selection for Mobile theme to switch to desktop theme display.
Option 1. Mobile site using subdomain
http://drupal.org/node/1214890 using apache to rewrite
Need to convert it for nginx rewrite
Option 2. Mobile site using theme
http://drupal.org/node/629520#comment-3941580 using boost to cache mobile theme using apache rewrite.
I hope to have a discussion on how to create a light weight nginx redirect mobile and desktop