What part did they innovate?
UX.
Long ago an industry-leading naysayer opined of the iPod "no wireless. less space than a Nomad. Lame."
, however, got the user experience RIGHT, and the
Watch is the descendant of that (a hundred billion dollars cash under the mattress later ... and what's a Nomad?). It's not that any particular aspect is outstandingly awesomely undeniably innovative, it's that they put the right innovation together into something that will take over the "smart watch" industry overnight.