How about we just take the empirical test. I know I often forget to turn off my iphone on the plane (1 out of 5 times I fly). I'm not alone, and there are 100+ people on the plane. Odds are very good that we have thousands of hours of real world tests with a dozen phones turned on.

If this were actually a serious problem for the plane, there would already be a sensor for this. "Sir, there's something emitting radiation in your pants".