Vague question, as privacy means different things to different people, but its very hackable, so as long as you're running Android you should be able to make it work how you want.

By default it uses the Pebble App for sync. You can decide whether that meets your privacy needs or you want a custom app. Someone has probably shared how to do what you want.

See the other trending HN post for Apple compatibility (TL;DR it sucks because Apple makes it suck).