The optical sensor use for Heartrate monitor are nowhere near the level of having a strap around your chest. The GPS in your iphone will never beat a dedicated gps chip like in the Suunto and Garmin watches. It doesn't have water resistant level close to theses watches either. The fitness part is the novelty part of the watch. It also doesn't have the backend analysis once you upload your workout. Part of Suunto product is the movecount website. I am very skeptical so far that Apple Watch will get the same level of details/analysis. I have an Suunto Ambit 2 + heartrate strap and I will put it against the Apple Watch. I am willing to be more than willing to share the charts gathered by the 2 watches.