Just as the Band is not FULLY compatible with Android I.e.no Google Now and the Apple Watch won't be with Android or Windows.
Notice a pattern there?
Things like the Band and Fitbits are most compatible with all phones. Suggest you look no further than the Band.
The band is a fitness device, not a watch. I can care less about a fitness "look" of the band and have no interest in it. What I want is a watch that, well, looks like a watch, not something that has a little brick with a watch band or a fitness device.
Windows Phone is a major disappointment on this aspect, Even a Android watch that could work with WP with notifications or something would do but, of course, nothing really that looks remotely good.
I even had a Pebble at one point, to play with it because I could use a smartwatch, even a few 3rd party apps allowed you to do some things but, the basic things, it would not let you do. Yea, all I ended up using it for was a watch with some cool faces on it...I ended up selling it (made about $15 on it so, I'm good)...
Personally, I could care less about the Band's support for iOS or Android, yea, No google now but, on WP you get cortana, good, Microsoft should support their OS more than other devices....
Smartwatches are starting to look better (now that we are on the 3rd gen for models), longer battery life and a lot of style aspects not just fitting everything in a box for your wrist but, nothing for WP....