You never know when you might need a phone (particularly for emergencies). Frankly, I see little point to this device if it requires an iPhone to be useful. To me, the whole point of having a watch would be it's smaller and on my wrist instead of having to fish out the phone out of my pocket all the time (although I personally find watches uncomfortable over long periods of time and rarely wear them anymore so putting up with pulling out an iPod or iPhone seems preferable to some extent for that reason).
I think until they can make this device fully capable on its own without an iPhone, it's going to be very limited niche device. I mean what can it do that an iPhone cannot do? Look pretty on your wrist? There are better looking watches for that. I simply don't get it and unless other people do, I don't see what market this is meant for (people who have everything and still want more, I suppose). Devices should have clearly defined functions and other than telling time and being slightly faster to look at than pulling a phone out of one's pocket , it seems utterly utterly pointless and merely an alternative to an iPhone, yet by REQUIRING ONE, it completely defeats the point, IMO. I suppose it would be useful in business meetings to read text messages and other data without being obvious that you're not paying attention to the boss, but that just makes it yet another potentially dangerous distraction, both at work and in cars and everywhere else.
I'm sure they'll sell a bundle of them anyway. Apple seems to be to be a status item in some circles (why else would anyone even consider shelling out $10k for a diamond encrusted one with still only 8GB memory on it that will totally outdated in 9 months time??? For the millionaire/billionaire who has everything I suppose.)