ActiveResource PATCH with ActiveModel::Dirty. Redefine 'update' to use PATCH instead of PUT. To have a true PATCH we only want to send the changed attributes. We tap into ActiveModel::Dirty's use of 'attribute_will_change!' method before saving the object. This writes changes to the 'changes' hash in our update method.

active_resource.rb

class ActiveResource::Base
  include ActiveModel::Dirty

  def update_attribute(name, value)
    self.send :"#{name}_will_change!"
    self.send("#{name}=".to_sym, value)
    self.save
  end

  def update_attributes(attributes)
    attributes.map{|k,v| self.send :"#{k}_will_change!" }
    load(attributes, false) && save
  end  

  # Update the resource on the remote service.
  def update
    run_callbacks :update do
      updates = {}
      changes.map{|k, v| updates[k.to_sym] = v[1] }

      encoded_updates = updates.send("to_#{self.class.format.extension}")

      connection.patch(element_path(prefix_options), encoded_updates, self.class.headers).tap do |response|
        load_attributes_from_response(response)
      end
    end
  end
end