I defer the discussion of whether or not the devices have any usefulness to the average consumer (I'm quite sure that they don't), and instead point out the lack of professionalism of the average "Professional Electrical Contractor" as evidenced in:
It seems, from my point of view, that the "professionals" a consumer would employ to install such a device (not the engineers to who I am speaking here) are scamming the public just as the sellers are.
So perhaps the real engineers here should be warning those who travel this way in search of more information, that both the sellers and the contractors will be very happy to take your money. Professionals? Phooey!!!