acts_as_smsable.rb

  module ActsAsSmsable
    def self.included(base)
      base.class_eval do        
        has_many :participants_sms_messages, :as => :participant, :dependent => :destroy
        has_many :sms_messages, :through => :sms_messages_participants do
          def sent_to(*args)
            conditions = args.map do |obj|      
              composite_key = "("
              composite_key += "participants_sms_message.participant_id = #{obj.id}"
              composite_key += " AND "
              composite_key += "pariticpants_sms_message.participant_type = '#{obj.class.base_class}'"
            end

    
            all :conditions => "(#{conditions.join(' OR ')})"
          end
        end
        
        has_many :sent_sms_messages, :as => :sender, :class_name => "SmsMessage"
      end
      
      def can_receive_sms?
        phone.present?
      end
      
      def to_sms_address
        if phone && name
          "#{name} <#{phone}>"
        else
          phone
        end
      end
    end
  end


# 
@user.sms_messages.sent_to(@someone) # Undefined method error!