Zoll LifeVest is a Class III , FDA requires PMA submission, for example implantable pacemaker, pulse generators, HIV diagnostic tests, automated external defibrillators, and endosseous implants.
This device also is used to help sustain life, which means high risk, so definitely will be Class III.
And, also, according to FDA definition for mobile medical apps:
Any Mobile apps that allow a user to collect (electronically or manually entered) blood pressure data and share this data through e-mail, track and trend it, or upload it to a personal or electronic health record.
or the app be used as an accessory to a regulated medical device; or To transform a mobile platform into a regulated medical device, will be considered as a mobile medical app.