title: Rails 3 detect request coming from mobile clients
body: <p>My setup: Rails 3.0.9, Ruby 1.9.2</p>
  
  <p>My app needs to serve up a mobile vs. web layout depending on the request's origin. I need to support all the major mobile client front-ends like iPhone, Android, Blackberry, etc. What's the simplest way to detect this in my code?</p>