I have written a mavproxy module that outputs depth, temperature, and heading on a udp port. To use it, install mavproxy from the source code here.
Extract the code, go into the top-level directory, and run the setup.py script:
python setup.py build install
To use mavproxy (auto-connect udp must be disabled in qgc settings, qgc must be set up to talk on a new comm link at port 14551):
mavproxy.py --master=udpin:0.0.0.0:14550 --out=udpout:0.0.0.0:14551
After you start mavproxy, enter the command module load DepthOutput, and the data will start being sent to local port 25102.