I've had the alarm go off according to the parameters that I set in the Relay module but I don't think anything else happened other than the alarm. The coach was still receiving power and the batteries seemed to continue getting charged. The alarm was for over current to the batteries during charging.
The Relay can be used to control a larger relay or other device. It is only rated to 1 amp so cannot handle the full load of your system. It can be used to control a battery protect for up to 220 amp.
Depending on what else is in your system it might be able to control other devices in your system.
Yes the relay can be used to control external devices. Unfortunately support for how to turn the relay on or off is severely lacking. You can do some basic automated stuff (turn the relay on if the voltage goes below a threshold for instance) but any use that isn't specifically addressed in the user manual of the BMV is difficult or non existent. Too bad because there's so much potential to do creative things with that system.
Right now I have mine setup to remote turn on a large inverter, but I have to jump through silly hoops to use the function because Victron doesn't allow the relay to just be manually controlled from the Cerbo or their other remote management devices.
If you install the Venus "Large" OS on a Rasberry Pi and using Node RED, you can manipulate it how ever you want. It's pretty awesome.
