This is a basic adapter for ActiveResource to (mostly) work with Devise.

1. Add this as a submodule or stick it somewhere that will be loaded by Rails
2. Set Devise to use this by requiring active_resource_model in config/initializers/devise.rb
3. Subclass your model from ActiveResource::Base & include any ActiveModel components you want to use
4. Figure out which methods to override...

Initially we found it necessary to over #save to set some of the attributes you want to pass along. Here's an example with database_authenticable

class User < ActiveResource::Base
  include ActiveModel::Validations
  include ActiveResource::Validations

  self.site = "http:g/localhost:9292"
  self.format = :json

  attr_accessor :encrypted_password, :password_salt

  devise :database_authenticable

  def save
    self.password = @attributes['password']

    # make sure encrypted password gets set
    raise "encrypted password not set" unless @encrypted_password
    @attributes['encrypted_password'] = @encrypted_password
    @attributes['password_salt'] = @password_salt

    # delete the keys you don't want to pass back
    @attributes.delete('password')
    @attributes.delete('password_confirmation')

    super

    # manually load the errors
    self.load_remote_errors(@remote_errors)
  end

  # override some of Devise's methods
  def active?
    super && special_condition_is_valid?
  end

  def special_condition_is_valid?
    false if @errors
  end

  def special_condition_is_not_valid
    @errors.full_messages
  end

  def inactive_message
    special_condition_is_valid? ? super : :special_condition_is_not_valid
  end
end

That's about as far as we got, which was getting success messages & errors back from the remote server just like you'd expect from using ActiveRecord.

Copyright Jesse Cooke (not that I really care) and released under the MIT license. Special thanks to Ed Phillips for figuring out the errors stuff.