houhoulis/rack-uri-loader

This Rack middleware (rack-uri-loader.rb) is intended to serve an
external Web resource as though it were local, allowing further
transmogrification.

If you set your rails app to serve a view as text rather than as html,

  render :text => "http://www.yahoo.com", :content_type => "text/plain"

then this middleware assumes you are giving it a URL.  The middleware fetches
the URL and serves up the resource in that view of your application.

(techiferous's rack-plastic, http://github.com/techiferous/rack-plastic,
is a complementary middleware which you could use to facilitate further
Nokogiri manipulation of the page to be rendered.  It was part of the
inspiration for this middleware.)