Done right, I think it could be interesting. It would need to be fairly compact so as not to look ridiculous, like most existing uber-watchings. And inductive-style charging would be nice, so you wouldn't actually have to plug it in (like the new Nokia Lumia wireless charging system - toss the watch on a pad to charge at night). I think some key features would be:
* Speakerphone & vibration function
* See who is calling, answer/block
* Read text messages
* Time & weather display
* Newsfeed (something like notification center - email headers, RSS headers, etc.)
I'm not quite sure how the text message thing would work, because the screen would need to be Retina to have really clear fonts, but even then, you'd need a larger and/or wider screen for it to look halfway decent, without doing massive line-wrapping on longer messages. But for sure, something that could buzz on my wrist when I'm in a meeting or in class so I could glance down and see who's calling, read a text message, or check an email header would definitely be welcome - not have to slide the phone out.
A color e-ink screen would also be novel...that way it wouldn't have to light up the room when you get a notification and you're in a darkened room watching a PowerPoint presentation. Something with a backlight like the new Kindle Paperwhite would be slick. There's been a lot of interesting technologies as mentioned...the Nike Fuelband, the Pebble smartwatch, and other neat things like the Jawbone Up:
https://jawbone.com/up
A band that you could wear 24/7 to track your sleep, heartrate (pulse), step count (pedometer), etc., plus give you notifcations and stuff would be really slick. I could see that being pretty big, actually.