Its a bad idea, full stop. Its a watch that requires a phone to be of any real value....at a time when most under 30 look upon a watch as a throwback to the days of disco.
Both of my boys are in their early 20s, neither have owned a watch...why? Because they have been surrounded by things with clocks built in since birth, that's why. I work less than a mile from the local college so I work around college kids all day...damned near zero watches, why? They already have a smartphone AND a tablet AND a laptop AND a clock in their cars....WTF they need a watch for? Hell I'm nearly 50 and haven't worn a watch in over a decade, the wife is 7 years older than me and doesn't even own one, that is what the phone in her pocket is for.
It just shows IMHO that Apple has run out of ideas as all the previous hits of the past decade plus, iPhone,iPad,iPod,etc were all things that people already used and had uses for that had bad UIs, the watch? The few people I know who refuse to let go of their watches are traditionalists that value things like Swiss movements and have NO desire to add high tech crap to their wrist, the rest? Well as one group of college kids in the shop said when the first talk of iWatches came up "If I have to have my phone...what do I need the watch for?". I couldn't think of an answer then other than "to give something for Apple to sell to hardcore fanboys" and I still can't come up with anything else, as for an ever growing segment of the population a watch belongs next to a rotary phone in the dustbin of history.