While case-by-case circumstances can effect the practicality of many alternatives, there are external pacing and monitoring options. The Zoll Company for example has just released a type of vest, worn similar to a brassiere with a fanny pack (battery pack). This device consistently performs cardiac monitoring and when a shockable rhythm presents itself the device does just that. More archaic methods would involve adhesive defibrillation or subcutaneous pacing patches and a cardiac monitor, while the monitors can be significantly expensive, older models are available at online auction sites. Both the aforementioned devices can be recharged, and more importantly, stored in a Faraday cage to protect them from an EMP. Neither would be as convenient as implanted devices but in a pinch could be just the thing to keep that ticker going. – John, EMT-P.
You aren’t safe even when it is not an EMP. See this Vice article. 
Furthermore, no wireless devices are likely to be safe, including Simplisafe. 
Don’t trust anything wireless for anything important.
Regards, – T.Z.