"Here comes a late reply for others who find this thread.
About the arming notifications I don't know about sound, but found a guyd how to easily add external leds to show the statushttp://www.rcgroups.com/forums/showpost.php?p=24149173&postcount=398"
"Interesting.I'm having similar thought.About the gyros i assume with no wind it should loiter fine. Looking at the code to see what i can find out about the sonar.Let me know how you've succeeded/ Patrik"