It will be interesting when hearing aids have radios built into them (as they soon will have) for various reasons. How will anyone except the user know if the thing is transmitting?
Fortunately, the power will be low enough that there shouldn't be a problem - you can see that a non functioning hearing aid has the potential to be quite dangerous in an emergency situation. Of course, the one piece of electronics that passengers aren't told to switch off is the pacemaker! (A CAA guy I know said that this was because the paperwork at the CAA would be too much if it happened!)