Protecting personal computers (PCs) from unauthorized access typically relies on password authentication, which is known to suffer from cognitive burden and weak credentials. As many users nowadays carry mobile devices with advanced security features throughout their day, there is an opportunity to leverage these devices to improve authentication to PCs. In this paper we empirically evaluate a token-based, passwordless approach in which users authenticate to their PC by confirming the authentication request on their smartphone or smartwatch. Upon a request to login to the PC, or to evaluate privileges, the PC issues an authentication request that users receive on their mobile devices, where users can confirm or deny the request. We evaluate button tap and biometric fingerprint verification as confirmation variants, and compare their authentication duration, success rate, and usability to traditional password-based authentication in a user study with 30 participants and a total of 1,200 authentication attempts. Smartwatch-based authentication outperformed password-based authentication and smartphone-based variants in authentication duration, while showing comparable success rates. Participants rated smartwatch-based authentication highest in usability, followed by password-based authentication and smartphone-based authentication.