I Have an USB-Bluetooth-Stick which for my Laptop. Since the stick is not always present at the Laptop I only want gnome-obex-server to run if the bt-stick is really there. To do this I use a simple script and an udev-rule:

/etc/scripts/obex

  #!/bin/bash 
  case "$ACTION" in 
    "add") 
      (export DISPLAY=":0.0" && sleep 4 && su seiichiro -c gnome-obex-server) &
      ;;
    "remove")
      killall gnome-obex-server
      ;;
  esac

(note: seiichiro should be replaced with your normal X11-User)

and finally the udev-rule that make all the magic happen (insert them into your lokal udev-rules):

KERNEL=="hci0", RUN+="/etc/scripts/obex" 

After this gnome-obex-server should start and stop itself whenever the BT-Stick is inserted/removed Note: this only works for a single user, for multiple different users a more complex script would be necessary.