Everyone hates it when some jerk's cell phone goes off in the middle of a conference or meeting or movie. Most people are embarrassed when theirs does it.
The Phonekerchief is a good solution because it uses thin metal fibers woven into a neat-looking napkin to block the radio signals that link you to the meta-net. (I'm just assuming it works, btw; I haven't tried it, but have seen other jury-rigged Faraday Cage adaptations work to block WiFi, RFID and cell signals.)
Technology Review suggests using the signal-smothering napkin to keep Thanksgiving dinner text- and ringtone free.
The fatal flaw with that idea, and any using a passive blocker like a napkin or wallet made from steel or duct-tape, is that they silence the least-annoying phone in the room -- yours. What you need is something that silences other people's phones. Cell phone jammers work well enough, but are a little illegal in many places, so you probably don't want to be too obvious about using one in public.
You also don't want to do it, or at least be the kind of person who does that kind of thing.
It doesn't happen that often anymore, but at one point I rarely went a month without hearing a network manager talk about problems shutting down access points or wireless access to conference rooms because some manager thought it would be easier to get people to pay attention if they had no access to email, data or online apps.
It works, but in the same way the character-building discipline bad football coaches and assistant high school principles impose on teenagers -- it gets people to behave while they're being watched, but resent having their freedom of choice taken away. They end up acting out in other ways.
At big family holiday gatherings where sensitive topics may already be simmering beneath the surface, letting people take or make phone calls or texts might actually make the whole thing more peaceful, or at least not make them thing you're a little too patronizing and anal to be invited to more optional family events.
It's your call. Silence your own phone and be annoyed by theirs, or silence their phones and be annoyed by them.
Or you can just skip both things, turn off your ringer and dig in. Critical as good data and communications networks are, for a couple of hours before the football game, they don't hold a candle to unfettered access to turkey, stuffing and gravy.