$ yaourt mpd noti                 
1 aur/indimpc-git 20121107-1 (5)
    Minimalistic MPD client with support for multimedia keys and notifications
2 aur/mpd-notification 0.7.0-1 (5)
    Notify about tracks played by mpd
3 aur/mpd-notification-git 0.7.0.r0.g14c059a-1 (0)
    Notify about tracks played by mpd - git checkout
4 aur/mpd_notifyd 0.16-1 (0)
    Notifier daemon type for MPD using libnotify. The start of reproduction is reported.
5 aur/mpn 1.1-2 (5)
    MPNotifier is a lightweight client for MPD displaying a popup notification each time a new song is played

mpc idleloop player | while read event ; do notify-send "$(mpc -q current)" ; done

#!/usr/bin/env python3

HOST = 'localhost'
PORT = 6600

import os
import mpd
try:
    from gi.repository import Notify
    notify_init = Notify.init
    Notification = Notify.Notification.new
except ImportError:
    from pynotify import init as notify_init, Notification


def notify(song):
    notification_parts = []
    if 'artist' in song:
        notification_parts.append(u'{artist} - '.format(**song))
    if 'title' in song:
        notification_parts.append(song['title'])
    elif 'file' in song:
        notification_parts.append(os.path.basename(song['file']))
    else:
        notification_parts.append('<untitled>')
    notification_text = ''.join(notification_parts)
    notification = Notification('Now playing:', notification_text)
    notification.set_timeout(20000)
    notification.show()


def watch():
    notify_init("MPD - now playing")

    client = mpd.MPDClient()
    client.connect(HOST, PORT)

    current_song = None
    while True:
        client.send_idle()
        changed = client.fetch_idle()
        if 'player' in changed:
            client.send_currentsong()
            song = client.fetch_currentsong()
            if song != current_song:
                notify(song)
                current_song = song


if __name__ == '__main__':
    watch()

mpc idleloop player | while read event ; do notify-send «$(mpc -q current)» ; done