If you do not comply after several warnings, an alarm would sound that would make conversation impossible for a few minutes.
If you want it for your own home it's likely not that difficult to set up on a technical level, but I suspect it might not go down too well with any visitors.
If a computer presumed to tell me how loudly to talk, I would have it recycled.
The computer is my servant, not my mistress.
And honestly, it seems better that kids hear it from other people, rather than machines. Because kids need to learn to respect other people's boundaries in a shared space. A lot of parenting is actually you modeling asserting your own needs so they know they can do the same.
I mean when our washing machine goes into its death spin cycle, we don't stop talking.
Instead we up the volume or move away and enjoy the benefits of the inverse square law at 6db per doubling of distance.
On the other hand, it sounds like a great jumping off point for a Youtube channel. https://www.youtube.com/c/simonegiertz