implanted electrical device would be a problem I would think.

And they are becoming more common.

I personally cannot tolerate magnets on the neck or on the head. They make
me dizzy. Even the small ones. So I don't recommend them there, since they must be stimulating some nerves for me.. and who knows what nerves other people are having problems with?

But I do use them on the hands and legs/feet for severe pain. I've had them for years. Worked really well with my broken toe, no swelling/no throbbing pain.
The podiatrist was surprised to see the xray, the 2nd day after, when the toe
looked normal..even the nail was not bad, but it did fall off later. They require alot of experimentation, and moving around to find the best place. Not unlike the Lidoderms that way