Fitbits work, but not with the same level of features as with IOS/Android. I have the Charge 2, and there is no option for connected GPS in the Windows app, and notifications don't work.
Garmin devices work, but notifications are shaky. Sometimes they come through, sometimes they are delayed, and sometimes they don't make it through at all. Device sync sometimes takes 2 or 3 tries to succeed.
To my knowledge, there is nothing that compares with the Band when it comes to Windows mobile compatibility. Now that the Band is going away, so is my last real reason to hold on to the platform. IMO, Windows Mobile has just about succumbed to 'death by a thousand cuts'. Very disappointing.