Drivers can't "talk" to each other directly unless they have a parent/child (or sibling via the parent) relationship, so you'd either need that or an app.
As you've noted, there are existing solutions out there. Here is one:
Even if you don't use that, perhaps it would give you a starting point.
Or if you've already got everything else figured out, maybe just add flipping the state of both switches to your existing app (or rule)?
