n900_headset_button_monitor.py

#!/usr/bin/env python

class HeadsetButtonMonitor:
  def __init__(self):
    self.bus = dbus.SystemBus()
    obj = self.bus.get_object('org.freedesktop.Hal', 
        '/org/freedesktop/Hal/devices/computer_logicaldev_input_1')
    iface = dbus.Interface(obj, 'org.freedesktop.Hal.Device')
    iface.connect_to_signal("Condition", self.handler)
	
  def handler(self,arg1,arg2):
    print "HeadsetButtonMonitor: got headset switch (%s, %s)" % (arg1, arg2)

hbm = HeadsetButtonMonitor()