gistfile1.rb

# in /config/devise.rb
...
  # Configure the class responsible to send e-mails.
  #config.mailer = "Devise::Mailer"
  config.mailer = "MailerWithInfo"
...

# in /lib
class MailerInfo
  def self.attributes=(attributes={})
    Thread.current[:mailer_params] = attributes
  end

  def self.attributes
    Thread.current[:mailer_params]
  end
end

# in /app/mailers
class MailerWithInfo < Devise::Mailer 
  def setup_mail(record, action)
    atts = MailerInfo.attributes
    atts.each {|k,v| instance_variable_set("@#{k}", v) } if atts && atts.is_a?(Hash)
    super
  end
end