Rails 4.1 offers variants so that you can have different view templates depending on the display type. Here's a more thorough example. It's really recent so there's not a lot out there about them yet.
If you're not on 4.1, you can look at using the Mobylette gem to achieve the same thing. You can then also have a completely different application.mobile.erb
that includes different assets.
For flipping between which assets you're including, you can also take a look at this (the helper method part), but this won't address the issue with different sets of views across the board:
Mobile style switching in Rails 3, helper method vs media queries