I have one of these watches. While it is an interesting addition to my collection, and it is fun to follow the amount of daylight versus night time, moon phase, etc. it is not nearly as useful for serious photography as is The Photographer's Ephemeris app. for an iPhone or other device.
Much easier to "project" for future locations and dates w/ TPE. And what I've found is that even when I'm out of range of a cell signal in the boonies, if I've done my homework will have saved "screen shots" in my photos on the phone of time places, times, etc. that I intend to shoot.
If you do buy one of the watches, I'd avoid the black ones. That's what I chose, and the oxide coating on the band/bracelet rubs off way too easily. I'm pretty "easy" on my watches, so the wear isn't from abuse.
If you like clever watches, you'll enjoy it, but as a serious photographers tool, I find it limited.