countdown.exs

defmodule Countdown do
  def sleep(seconds) do
    receive do
      after seconds*1000 -> nil
    end
  end

  def say(text) do
    spawn fn -> :os.cmd('say #{text}') end
  end

  def timer do
    Stream.resource(
      fn ->     # num sec to start of next min
        {_h, _m, s} = :erlang.time
        60 - s - 1
      end,
      fn       # wait for the next sec, then return its countdown
        0 -> {:halt, 0}
        count -> sleep(1)
        { [inspect(count)], count-1}
      end,
      fn _ -> end # nothing to deallocate

      )
  end
end

counter = Countdown.timer
printer = counter |> Stream.each(&IO.puts/1)
speaker = printer |> Stream.each(&Countdown.say/1)
speaker |> Enum.take(5)
Countdown.timer 
|> Stream.each(&IO.puts/1)
|> Stream.each(&Countdown.say/1)
|> Enum.to_list