Attached is a patch against udev-008 to send out a D-BUS message when a
device node is added or removed.

Using D-BUS lingo, udev acquires the org.kernel.udev service and sends
out a NodeCreated or NodeDeleted signal on the
org.kernel.udev.NodeMonitor interface. Each signal carries two
parameters: the node in question and the corresponding sysfs path.

[Note: the D-BUS concepts of service, interface, object can be a bit
confusing at first glance]

An example program listening for these messages looks like this

#!/usr/bin/python

import dbus
import gtk

def udev_signal_received(dbus_iface, member, service, object_path, message):
    [filename, sysfs_path] = message.get_args_list()
    if member=='NodeCreated':
        print 'Node %s created for %s'%(filename, sysfs_path)
    elif member=='NodeDeleted':
        print 'Node %s deleted for %s'%(filename, sysfs_path)

def main():
    bus = dbus.Bus(dbus.Bus.TYPE_SYSTEM)
    bus.add_signal_receiver(udev_signal_received,
                            'org.kernel.udev.NodeMonitor',  # interface
                            'org.kernel.udev',              # service
                            '/org/kernel/udev/NodeMonitor') # object

    gtk.mainloop()

if __name__ == '__main__':
    main()

and this is the output when hot-plugging some usb-storage.

[david@laptop udev-008]$ ~/node_monitor.py
Node /udev/sda created for /block/sda
Node /udev/sda1 created for /block/sda/sda1
Node /udev/sda1 deleted for /block/sda/sda1
Node /udev/sda deleted for /block/sda

The patch requires D-BUS 0.20 or later while the python example program
requires D-BUS from CVS as I only recently applied a patch against the
python bindings.