I was going to follow up on HarryT's post by commenting that very few people realize that a mobile phone includes a radio transmitter, but you pretty much made the point for me: anything with Wi-Fi includes a radio transmitter. Likewise for anything with BlueTooth. Ditto for many other wireless devices.

Transmitters are the biggest risk because they are of relatively high power. Many people don't realize that some receivers also create radio frequency noise. An example is heterodyne receivers, since they use an intermediate frequency before demodulating the signal. Heck, any electronic device will emit electromagnetic radiation. That's why so many devices carry FCC approval. On top of that, poorly designed equipment can create spurious signals at unintended frequencies. Look up radio harmonics for one such example.

I'm not going to pretend that I understand everything here because it is a complex subject that I haven't dealt with in a rather long time. Organizations like the FAA have a better understanding of the issues, so I'm willing to take their word on such matters. I am not willing to accept the word of people who feel inconvenienced by the regulations, and are unlikely to understand how electricity works.