David Greenspan was starting this possibility on google groups on Feb 2014
I’m not talking about redirecting to another site (mobile.mysite.com) – that’s silly – just using different (potentially very different) CSS and JS. I realize that for many sites/apps, activating some CSS based on the window size may be enough (that’s media queries, right?), but it seems like that would break down for richer apps.
What is the status for now? How to use different css and js for different device?