How did we come to watches? Watches are not only time-keeping gadgets (and they are good at that), they are fashion items. And all the people around me (class/work) have watches.
We can discuss on 20 pages how each one of the mentioned appliances does its job better than when applied in a phone. Yet when i go out, I check that I have 3 things in my pocket - phone, keys and wallet. Sometimes it happens that I need a gps or a e-reader or a camera or calender (or whatever) with me when I am on the go, and I forgot to take such on the way out. If the feature weren't implemented in the phone, I'd have a big problem. And when we are talking of GPS or camera it could be a BIG problem.
I haven't yet been through a day that have killed my battery entirely. Charging once a day is more than enough and spare OEM battery cost $4.
BTW - my phone has substituted my home DVD player. I use a TV out cable and watch movies on the TV through my phone.
The next step as I see it - having my wallet and documents on the phone and in the long run - my keys too. Having only two big toys in the pants will be great
