Device detection in apache

As maintainter of the Drupal Mobile Tools module I often get the question how device detection works when caching is enabled (e.g. with Boost).

Several solutions are emerging. Two of them worth looking at:

- http://www.projectronin.com/blog/?p=10
- http://www.idelfuschini.it/en/apache-mobile-filter-v2x.html

Both are doing device detection in apache.