Follow these instructions with a couple differences:
For your case, in the above instructions/walkthrough change the rule trigger to be when the VDBv2 button is pressed and the action to be turning on a different camera you have (or a plug or something). Then you have Google watch for that device to get an “On” command sent to it and tell it to make an announcement any time that happens.
If any of that is confusing, let me know and I’ll rewrite the steps here to make it more clear.