I have not seen any confirmation by any source (other than the manufacturer) that those things work. Its also counter-intuitive...how could an electrical field affect the positive or negative charge on an ion. Those charges are teeny, but at the atomic level, they are huge. Those charges are much larger than the electrical field.
By the way, this scam has been going on for decades. Do try and keep your money in your pockets and save it for a RO system.
Another system you might see is based on using Citric acid to reduce hardness. That system does actually work because citrate causes metallic ions like Ca to chelate and effectively removes them from the water chemistry. Now, that chelated calcium is still in there, it just can't do anything. The acid part of the citric acid also neutralizes some of the water alkalinity. The problem with that system is that you'll spend a fortune on citric acid. So its not really too viable, but it does work. Again, save for RO!