Uses pyserial and py-libmpdclient.

#!/usr/local/bin/python

import serial,time,mpdclient

class RetryingMpdController:
    def __init__(self,**kw):
        self.mpd_kw = kw
        self.reconnect()

    def reconnect(self):
        self.mpd = mpdclient.MpdController(**self.mpd_kw)
        print "connecting to mpd"

    def __getattr__(self,attr):
        def retrying_method(*args):
            func = getattr(self.mpd,attr)
            try:
                func(*args)
            except mpdclient.MpdError:
                self.reconnect()
                func(*args)
        return retrying_method

class Pedals:
    """
    connect RTS to DSR and CTS like so (pin numbers are for 9-pin
    serial port):

    pin 7 RTS -->-----------+
                            |
                left   /    |
    pin 6 DSR <-------/ o---+ 
                            |
                right  /    |
    pin 8 CTS <-------/ o---+
    """
    def __init__(self,*actions):
        self.ser = serial.Serial(port="/dev/ttyS0",rtscts=1)
	self.ser.setRTS(1)
        self.prev = False,False
        self.actions = actions

    def poll(self):
        pedals = self.ser.getDSR(),self.ser.getCTS()
        for which in range(2):
            if pedals[which] and not self.prev[which]:
                self.actions[which]()
        self.prev = pedals

class Playback:
    def __init__(self):
        self.mpd = RetryingMpdController(host='localhost',port=6600)

    def rewind(self,secs=2):
        pos,length,frac = self.mpd.getSongPosition()
        self.mpd.seek(seconds=pos-secs)

    def pause(self):
        self.mpd.pause()

play = Playback()

ped = Pedals(play.rewind, play.pause)

print "monitoring pedals (press ctrl-c to exit)..."
while 1:
    ped.poll()
    time.sleep(.01)