The Lifevest would have to be a Class III because it has the potential to save a life, though is a great risk to the wearer. Because the response of the mechanism is based off the persons heartrate, there is concern for what conditions would warrant a defibrillator, so I would recommend talking to the physician to make sure an ICD wouldn’t be better.
Undoubtly this device went through some intense clinical trials to verify the safety. Not only does it have to be successfully able to detect a heart rate, abnormal at that, but also respond with the correct voltage and pressure in the proper locations. There’s also the concern of environment, i.e. to make sure the device doesn’t short circuit or decalibrate (?) is someone say spills water on themselves.
The mobile app is an interesting idea, but I think it would be better if the device was able to call for help like AARP or a hospital when triggered.