While mobile devices frequently require users to authenticate to prevent unauthorized access, mobile devices typically do not authenticate to their users. This leaves room for users to unwittingly interact with different mobile devices. We present GoodVibes authentication, a variant of mobile device-to-user authentication, where the user's phone authenticates to the user through their wristwatch vibrating in their pre-selected authentication vibration pattern. We implement GoodVibes authentication as an Android prototype, evaluate different authentication scenarios with 30 participants, and find users to be able to well recognize and distinguish their authentication vibration pattern from different patters, from unrelated vibrations, and from the pattern being absent.