First part - http://www.personal-view.com/talks/discussion/12604/smart-watches-apple-sony-and-samsung-doing-strange-things#Item_2
It is important to note one thing considering smart watches. Most of them need functioning Bluetooth 4.0 LE.
And even if you phone has Bluetooth 4.0 in the specs it does not mean anything.
One of the best phones for watches now is older Galaxy S3 and S4, both have updated firmware and work ok with most watches.
No Android 5.1 builds are under development for the Galaxy Note 4 or any other Samsung device
It looks like you're new here. If you want to get involved, click one of these buttons!