Cell phones are safe if: You do not disconnect the battery in a hazardous location. The standards for being clasified intrinsically safe madate that any electrical connection that can be seperated must have a mechanism to shield the contacts from the atmoshere and that it takes a physical action to disconnect. Look at your test equipment and radios, all the battery disconnects are shielded and communication ports have a twist on/off connection.
The reason there are few intrinsically safe cell phones (I've seen them advertised) is that there is no money in it. It takes a lot of time and effort to have a devise certified that most cell phone makers don't need to cell phones. By the time a cell phone gets certified, it will be two generations out of date and the public won't buy it.
The same goes for non flash cameras, pda's, it's a silly as those devices on an airplane. In europe, cell phones are allowed during flight.