That said, no one should use a jammer. They are illegal in the US and that will expose the user to fines and potentially jail time. There are also legitimate times where someone might need to use a phone (emergency either at the performance or related to that person). As an example a friend of ours was an anesthesiologist who had to be 'on call'. There phone wouldn't ring but it would vibrate and they would leave if there was an emergency.
When I have been in a live theater that was disrupted (briefly) by a person using a phone, the effect response was to have the ushers escort them out and not let them return until after intermission, or if past intermission or no intermission, after the performance finishes.
Let people know before the show starts the consequences, and execute on those consequences when necessary. It seems to keep people respectful.
I can’t do any of that for you.
However, I can observe that there are passive means of blocking most radio signals (e.g., paint, wallpaper, aluminum foil, etc...), and those may not be illegal in your area. Again, you should consult your local lawyer.
Signal jammers work by producing the same radio waves that other devices produce, but with a lot of noise in them.
So it seems like if a signal jammer would interrupt a pacemaker's function, so would being near those devices that produce the signals but aren't signal jammers.