Hi Glenn,
You could also create a simple a bash script that monitors the F5's log file(s).
You can create a script that does an infinite while loop and sleep every X seconds, or create a script that is called from the crontab on the F5.
The script would just need to check the logfile with cat and detect which lines are 'new' since the last time it ran. Then for all of those 'new' lines check if a failover event has occurred and execute the script on your linux box through ssh. (just use a key without a password and setup ~/.ssh/authorized_keys on your linux box.
Kind regards,
Thomas