I've been wondering how good the continuous readings were on it. I'm actively considering the best device to track my really complex heart rate issues (I have postural tachycardia).
But I don't use an iPhone, so Watch might be off the table for the near future.
My personal experience is that the Apple Watch's heart rate readings are usually within 5 minutes of my AliveCor. Unfortunately, none of the Android watches currently on the market have a sensor that's particularly reliable. For now, I'd say a Garmin device or an AliveCor are the best bet for non-iPhone users.
But I don't use an iPhone, so Watch might be off the table for the near future.