Death Ray Mobile Phone?
The urban myth about cell/mobile phones as "unsafe" is the product of the conservative certification philosophy inherent in FAA/CAA approval of designs. Since it has not been shown that all manufacturer's mobile phones broadcasting on all frequencies can be tolerated in any airliner, no mobile phone operations are permitted. This does not mean they are unsafe, it just means they are unproven. Unproven is not unsafe.
In fact, to my knowledge (I have for the last 35 years made a living building and certifying flying machines) there has never been a demonstrated case of a cell phone ever affecting an aircraft system in any way.