Isn't a problem, there is a EUROCOPTER paper some years ago. But the paper investigated only the use of Defibrillators onboard the older ships like BO 105 and BK 117 (up to C1) and no problem was detected. Meanwhile we have the first EC papers of equipment failure up to FADEC problems due to the use of GSM phones (suspect). On the newer "space ships" i wouldn't recommend the use of Defibrillators.