You can't, at least not for all sites, there is no consistent standard for doing this, even if there were it is unlikely all sites would adhere to it. Our UK site uses http://hostname
/mobile, but the foreign versions use the same URLs for the same functionality.
Your best bet is to work through common scenarios and develop a flexible infrastructure that allows you to add new ones as they arise. If you have control of the sites you are going to track, you could add metadata specifying it is a mobile site and get that from jQuery