The effect of phones from a flight deck perspective
While mobiles may not effect the avionics noticably it is really distracting when we hear the electromagnetic interference when a passenger's phone (or sometimes my phone when I forget to turn it off) repetedly tries to log into the network as we enter range of a ground station. This usually happens on final approach into a really busy airport where radio communications are made every few second, and we need to hear them.
There is also a huge distraction factor during the take off roll when we are watching and listening for each others call outs and possible problems with the aircraft itself. Then, at a critical time (usually at just before V1) you get a buzzing in your ear followed buy the pulse repetitions from the phone in the overhead lockers above row nine under the VHF arials. For those reading who are not normally sat on the flight deck, that sound, can get the heart rate up if the timing is right.
Please, try to remember to switch off your transmitting devices. Thank you.