I got it to work!. Since I was not seeing any UDP traffic originating from the iPhone I assumed it was waiting to receive traffic from the APM via the bridge and maybe the bridge was not sending it. Further investigation revealed that the bridge was also waiting for traffic on port 14550 so neither side was talking. I simply changed the /etc/init.d/mavgateway file from this
DAEMON_ARGS=”–master=/dev/ttyUSB0,57600 –out=udpin:0.0.0.0:14550 –daemon”
DAEMON_ARGS=”–master=/dev/ttyUSB0,57600 –out=udp:192.168.1.9:14550 –daemon”
where the IP address above is the iPhone. I’ll do some further testing but it looks promising.