How many times have you been in church and during the sermon or during consecration or, well anytime during Mass and you hear someone's cell phone go off? It can probably be well asserted that most of the time a cell phone in church is wholly unnecessary. Most times because there can be incidents that require individuals to have their cell phones on them. As an example, a doctor who is on-call. Another example could be support personnel for a medical facility or someone awaiting emergency information from or about a loved one. That said, there is no reason the phones cannot be in silent mode. For anyone else, leave your cell phone at home or at least in your vehicle.
Now, if someone forgets to leave their phone outside or forgets to put it into silent mode and it goes off, one can sense the frustration in others. Is it really any more distracting than a child crying? Is it something we could just accept and not take offense to? It seems that some are overly annoyed by cell phones. We can all agree that any methods to avoid distracting others at church should be observed, but can we also make it our responsibility to refocus our attention as necessary when someone messed up and forgot to silence their phone? Consider the feelings of that person too - who now has the focus of many in their pews now on them - they are likely quite embarrassed and well aware of the distraction.
Another valid possibility of cell phones in church is the use of a smartphone app that contains the readings or even a full missal with rubrics to follow the Mass. Some will still frown upon someone using a "screen" in church, but in reality, what is the real difference between an electronic missal and a traditional book or booklet form? Still, if one wishes to use a smartphone app in church, they should do their best not to be distractive to others.