Detecting a mobile device in the bootstrap seems way too early for me. I haven't used Zend_Useragent yet, but what I know about the bootstrap is that it's there to *prepare* your application for running. So it wouldn't make sense to me to detect mobile browsers during bootstrapping. A front-controller plugin seems the best approach.
Have you tried my suggestions? It seems you should be able to write some quick logic in your plugin. In pseudo code: if [Zend_Useragent detects a mobile browser] AND [mobile view script exists] then update view renderer's view script suffix -- *Hector Virgen* Sr. Web Developer http://www.virgentech.com
