alarm_clock.rb

require 'music_player'
require 'timer'
class AlarmClock
  def initialize(music_player, timer)
    @music_player = music_player
    @timer = timer
  end

  def start
    @timer.start { @music_player.start }
  end

  def silence
    @music_player.stop
  end
end

music_player.rb

class MusicPlayer
  def initialize(mp3)
    @mp3 = mp3
  end

  def start
    at_exit { stop }
    @player_pid = spawn("cvlc #@mp3 2> /dev/null")
  end

  def stop
    unless @player_pid.nil?
      Process.kill('QUIT', @player_pid + 1)
    end
  end
end

set_alarm.rb

#!/usr/bin/env ruby
$:.unshift File.dirname __FILE__
require 'alarm_clock'
require 'pry'

mp3, *time = ARGV
time = time.join ' '
player = MusicPlayer.new(mp3)
timer = Timer.new(time)
alarm = AlarmClock.new(player, timer)
system('clear')
puts "Sweet dreams! You will be woken at #{Chronic::parse time}"
alarm.start
system('clear')
30.times { puts "WAKE UP! " * rand(1..5); sleep 2 }
60.times { puts "WAKE UP! " * rand(1..5); sleep 1 }
120.times { puts "WAKE UP! " * rand(1..5); sleep 0.5 }
Process.wait

timer.rb

require 'chronic'
class Timer
  def initialize(time)
    @time = time
  end

  def start
    sleep until_alarm(@time)
    yield
  end

  private

  def until_alarm(time)
    Chronic::parse(time) - Time.now
  end
end