I thought those millimeter wave sensors that are used in newer home automation devices to detect when people are in an observable area have enough resolution to detect the displacement of the chest during breathing, which would suggest that the tech you fear is already here, it's just not configured to record and analyze the data YET.
I would bet a large amount of money that this is already in use somewhere in the world. The idea is very similar to gait tracking and the tech has been available for years.
Yeah, it turns out if you can strap a device to somebody then wow you can identify them.
This is interesting, but not a big surprise!
Now if they can do this from an external passive sensor like a camera or microphone, then yeah that would be a neat result.