Received the GS3 yesterday got everything setup...logged onto my AT&T account to see if activation was necessary and was prompted to setup Numbersync. My unlocked Pixel was purchased from Google store, was told that (for now) Numbersync would not work on a non AT&T phone. I have confirmed that it does in fact work on a Google Pixel, messages and phone calls coming from the watch in standalone mode, show as coming from the phone....nice!