Okay, so cell phone interference, some observations:
They will sometimes make the bip bip bip sound, which could be annoying to pilots, I'll get back to that...
A part of my role in issuing STC approvals for modifications to aircraft is to qualitatively evaluate the modified aircraft for any electro magnetic interference (which would include cell phone interference). In the role, I spend a fair amount of time in the jump set of highly modified research airplanes, with a lot of special electronic gear, and some scientists in the back. Does any of that gear interfere with the plane or pilot's duties (story coming later...).
So there we are flying north from Inuvik in the Canadian arctic, with me listening on the headset, watching all the cockpit instrumentation, monitoring electrical consumption, and making lots of notes. Everything is fine, zero interference to the airplane systems, my job is mostly done, I'm along for the ride until we fly a practice ILS and do the final checks. In the intercom, I hear a gentle scientist's voice ask: "does anyone in the cockpit have their cell phone turned on?". Two pilots and I look at each other sheepishly - we all do. We turn them to flight mode, and report having done that - with a little embarrassment. The gentle scientist voice say thanks, they were interfering with our equipment. It would appear that the gear in the back was much more sensitive that anything in the cockpit!
In sitting jump seat, I'm right beside the avionics bay. In the just deliverd version of the plane, I remember having a rather annoying signal in my headset from the transponder. I checked with the pilots, and neither of then could hear it - it was just in jump seat - weird! I unplugged my headset to move to different jacks, and noted that even with the headset unplugged, I still heard the signal! With headset plugs in hand, I verified that I was not imagining this! I suppose it was some kind of induction from the transponder to the headset, with no electrical connection required. I ask that it be checked, simply out of radiation concerns for the crew. I guess it was fixed, 'hasn't done it since!
So, the story..... We had a newly designed radar system mounted to the belly to measure sea ice thickness in real time. This was powerful radar, so much so that it was not permitted to be operated on the ground - it would irradiate the crew! So the first test of this radar system would be the certification test I would ride along. I took the radiation meter, which I would wander around the cabin with, to check for radiation. We were given a specific line to fly over one of the great lakes (provided no boats were visible) by the authorities, as this radar was not to be operated over people at any altitude. So we're at the appointed start point, no boats. I give the okay to turn it on... three, two, one.... and an intolerable shreaking sound hit our headsets, and we all ripped them from our heads. Well... that didn't work! The radar scientists in the back did not need to hear me tell them over the headsets they were all holding that the test was a massive fail. We landed, went for lunch, while radar techs tuned things.
Next flight, same outcome: "Sorry, I cannot approve this system." " But... we're taking it to Greenland next week...". "Well, not approved, you can go with it turned off "(not much use for ice thickness measurement). So the next week, I was in Greenland, jump seat again, and the whole system was silent as could be. A pleasant run up and down the fjord, and all was fine. I signed the approval, marveled the beauty of Greenland, and headed back to Copenhagen. (By the way, there are not flights for Canada to Greenland, it is necessary to fly both ways via Copenhagen, so it makes for a long trip!