Devise - Autenticação por Token como parâmetro no Header

api_controller.rb

class Api::ApiController < ActionController::Base
  prepend_before_filter :get_auth_token
  respond_to :json

  public
  def restrict_access
    api_key = User.find_by_authentication_token(params[:auth_token])
    head :unauthorized unless api_key
  end
  

  private
  def get_auth_token
    if auth_token = params[:auth_token].blank? && request.headers["X-AUTH-TOKEN"]
      params[:auth_token] = auth_token
    end
  end

end

users_controller.rb

class Api::UsersController < Api::ApiController

	before_filter :restrict_access, :except => [:create, :login]

	.....

end