I took a couple photos of my arm/hand just a minute ago with the intent of doing a few photoshop mockups of what I think it could look like, but stopped before I got further. I just can't be bothered. I see 2 ways on how they could get a semi-clear projection on the hand like that.
1. Have the projector so far up the arm that it can project an image that's not too distorted. I'm talking half-way up the forearm. Nobody wants a watch like that.
2. Have it stick up from the arm really high, like those horrible TV watches. Or higher.
My day job for the last 13 years has been 3D artist, so visualizing how things
should look in "space", and how thigns visually interact with each-other is second nature to me, like breathing. It just can't work with the projector resting that close to the skin. It'll be a smear. The problem is the closer the projector is to the hand, and the closer it is to the skin, is you'll have an exaggerated angle. If you point near the base of the hand, the stretching will be lessened, but the projection will be partially obfuscated by bumps and hairs on your arm. It will be a really bumpy and hairy projection. You can point it up higher on the hand, less of your arm bumps/hairs will be in the way, but the smearing will just intensify.
If they'd market this as a bulky-ass box on a wrist with a blurry yet somewhat usable projection, then I'd have no issue with the campaign. Instead they have dark-emitting LEDs in high-def, no edge bleeding whatsoever, coming from an impossible angle. It's insulting.
I suspect that if they end up with a prototype, it'll look very much like that TV watch pic above, with the tiny projected numerals barely away from the watch.
If they had the money and the time/knowhow, they could do something REALLY fancy, like keep it small, then a mirror pops up from the top of the watch when you want to look at the time. That would keep the watch low-profile, and still provide the projection with a good "view" of the back of the hand. Though that's probably too much savoir-faire for these guys. Or indeed most people.