Not so simple. Required hydrogen gas as fuel, lots and lots of nickel tubing, potassium carbonate catalyst and of course electricity to heat the tubing, not to mention the device itself which had to have safety measures to ensure H2 gas didn't accumulate at the top and lead to potential explosion.
Given that overhead, and the device producing just watts of low grade heat (not electricity), it's not going to be marketable let alone something practical in the slums of the world. To its credit Thermacore took it a bit further from Mills' original idea but in the end still couldn't surmount the low power density inherent in that early iteration of hydrino chemistry.