Until a few months ago, I was under the impression that this rule was in effect as an anti-cheating measure, but when I asked an arbiter about this I discovered that I was wrong. The arbiter told us to turn our cell phones off or to vibrate, and when I asked about this discovered that the real point of the rule was to avoid distracting noises.
With that in mind, Nigel Short's sad plight makes more sense. Like Malakhov, he too had a cell phone problem, but unlike Malakhov he wasn't receiving a call (or a text message or whatever else one can receive from the latest crop of cell phones/PDAs/mini-computers). Enjoying a slightly better position against Ketevan Arakhamia Grant in something called the European Union Championships (not to be confused with the [stronger] European Individual Championship), his phone went off to "helpfully" indicate a low battery! It's not that he could have received any useful information about his game in this way, but it was a distraction, and so Short accepted the loss without complaint. Worse still, Short was sure he had turned it off; if so, then if this sort of feature is going to be universal to new phones, then we're all in trouble.
The main problem with the so called Smartphones are, some of them can only be put in standby mode, they never fully shutdown unless you take the battery out.