heroku.rb

require 'thin'
require 'sinatra'
require 'open-uri'

configure do
  set :server, :thin
end

get '/' do
  'index'
end

Thread.start do
  loop do
    open("http://aaaaa.herokuapp.com").read rescue nil
    open("http://bbbbb.herokuapp.com").read rescue nil
    sleep 60
  end
end