I've never seen a sleek, tiny watch that had GPS. The Fitbit Surge is the smallest I've seen and it's still pretty huge - more like a bracelet than a watch.
I don't know the nuts and bolts details but I think GPS has power/size requirements that preclude it from fitting in the size of something like a "normal" watch, at least until there's a major advance in battery technology.
Well, the watch isn't all that tiny, and Garmin does make a line of GPS watches similar in size to the 38mm watch.
I have no comment on accuracy, as I bought the expensive and much larger Forerunner 910XT. The current top of the line Garmin is the Fenix 3, which again is similarly-sized.
So, what I've heard -- and I'm not sure what the source was -- is that if you go for a few runs with your phone in your pocket, the Watch will be able to map the run without your phone, after it has learned your stride, etc.
I can't foresee GPS being a standalone component on watches due to battery drains. Garmin's watch currently gives me 10 hours on GPS, but that's also due to the fact that all it does is track my run.
Pictures of it on actual wrists here: http://www.cnet.com/news/fitbit-charge-charge-hr-and-surge-h...
I don't know the nuts and bolts details but I think GPS has power/size requirements that preclude it from fitting in the size of something like a "normal" watch, at least until there's a major advance in battery technology.