A:Answer As I understand it, if you have the cellular version, it will act as a standalone phone independent of an iPhone. But you must pay the carrier something extra about 20 bucks I think to get service on it.
However if you never leave home without your phone, then you probably don't need the cellular version, and they can just tie into your phone that you're carrying with you. Also this is the way you would have it at the house.
But if you're going to separate the watch from the phone beyond Wi-Fi distance between them, and want to watch to be a phone, you're gonna need the cellular version, as I understand it.