Is this a cyberattack, or pre-planted explosives?
My dad used to have one and it runs on single AA bsttery. It will burn if exploded but I doubt will that make "man fell on the groud bleeding." Newer models might use recharable batteries, yet the BMC (logically thinking) should be sperated from the communication part as charging have nothing to do with it. How are you going to use SMS to hack a part of the system which isn't connected?
If it is pre-planted explosives, that's just wet work and nothing to talk about it.
Of course, the attacker can do a supply chain attack (by threating/hacking the manufacture, excluding explosives) as a stage to make the cyberattack possible.