I think that they use the wrong kind of resonance... They should be using sounds, almost like cleaning jewelry with supersonic frequency, I guess, to give an example... but I think the current ones are magnetic. Unfortunately, cells will not respond to magnets very well, since we don't have a lot of metal inside us for the most part, so the sound would be the way to go.
Hopefully somebody can pioneer a version more akin to the originals based on sounds. It's an interesting topic, and I have no actual experience with it myself on a personal level. Some say they are helpful, but I think they are expensive, and need to focus more on sounds, and finding what sounds can do what, without harming other stuff in your body at the same time. I could be wrong, and maybe there are better ones out these days, but I think that most were or are using magnetic resonance.