The Verge noticed the similarity of the font used in Apple Watch presented yesterday and the Google Roboto font, which appeared in Android 4.0 almost three years ago. It is a simple, sans-serif font, which is easy to read on displays with low resolution.
Although Apple has recently applied a thin sans serif font Helvetica Neue in iOS and OS X Yosemite, but for some reason it did not used it in the smart watch interface. It is unlikely that Google will claim Apple, because Android L and Android Wear have been using a different version of the Roboto font, even more perfect, which is equally well-suited for screens with low and very high resolution.