It’s not trivial at all—finding a pacemaker/DBS-friendly massage chair is really important for your safety. Unfortunately, most massage chairs and vibration plates do emit electromagnetic fields, which can interfere with these devices. I haven’t come across any massage chairs specifically designed to be safe for people with pacemakers or DBS, which is frustrating.
As for covering the vibration plate with material that blocks emissions, it’s a creative idea, but I’d be cautious. Even if the material reduces emissions, if it doesn’t block them entirely, there could still be a risk. Since this involves your health, I’d strongly recommend discussing it with your doctor or a medical professional who understands how your DBS interacts with electromagnetic fields.
For everyday things like microwaves and phones, it’s true that emissions are everywhere, but the intensity and proximity matter. You might need to consider alternative relaxation options, like manual massages or other therapies that don’t involve electromagnetic fields, to stay on the safe side.