As a private pilot I've had to turn off GSM on tablets and phones to avoid interference in the headset. I still try to keep one cell phone on in case of an emergency.
There has been a few reported incidents with laptops etc causing interference with nav systems. While the rule may be too strict, I understand the "better safe than sorry" approach.
Search for "laptop" and you have a few examples of spurious TCAS RAs.
In some older report there was a specific instance where the pilot out of curiosity had the passenger turn the device back on, and had the problem reappear (this was in cruise so there was more time to debug the problem). Google for NASA PED reports and it should be in one of them.
Standard David Clark. I think it's a bigger problem with GSM which uses TDMA (the noise is caused by the cell phone transmitting only at specific intervals and therefore rapidly switching on and off, causing the buzzing noise).
There has been a few reported incidents with laptops etc causing interference with nav systems. While the rule may be too strict, I understand the "better safe than sorry" approach.