There's plenty of guidance material about ... however I would suggest that the following points are relevant for consideration ..
(a) some bits of kit can, and do, interfere
(b) if the EMI/EMR trials have been done and there is no demonstrated problem, then all should be well
(c) if trials haven't been done, then the main problem is passengers using untested kit without the knowledge of the crew
(d) it follows that crew use in the cockpit provides a simple control measure .. use is at sensible times and under appropriate MET conditions .. and, if something doesn't look quite right .. it is a simple enough check test to turn the kit off and see what happens.