I share skepticism about this being used in any serious way. An ultrasonic humidifier is going to be smaller, probably cheaper, and run laps around it in terms of output.
Disclaimer: I work for a company that makes low-cost air pollution sensors.
Also, as another poster pointed out, humidifying a large room in winter requires several liters of water per day. The cost of distilled water would quickly dwarf the cost of the humidifier itself, so other types of humidifiers besides ultrasonic (namely evaporative ones, where the main danger is mold, which distilled water doesn't help you with) are more economical.
And with the point being power-free, the air is going to be static or nearly so around the object (or bathtub). If it's supposed to get a boost from moving air from a forced-air furnace, that's cheating -- because in that case you could just install a similarly passive flow-through humidifier on that same furnace and be done with it, save perhaps an annual pad change. Many use no power, just the same "capillary and evaporation" as this - except with actual calculations underlying their specifications.