I agree with this list. As Siri gets smarter, it will be like everyone has a PA, not just executives, and the Watch will be the interface to that. And I'm sure it will get more sensors over time too. The Watch won't primarily be a communication device like a phone is, not all mobile devices have to be communication-centric. It will be something that monitors you through sensors and assists you through a digital assistant, as well as the identity function you mentioned.