Authenticating users on mobile devices is particularly challengingbecause of usability concerns: authentication must be quick and asunobtrusive as possible. Therefore, biometric methods seem well suitedfor mobile phones. We evaluate both speaker and face recognitionmethods on off-the-shelf mobile devices concerning their accuracy,suitability for dealing with low-quality recordings, and runningwith limited resources. Our results show that speaker and face recognitioncan realistically be used on mobile phones, but that improvements– e.g. in the form of combining multiple methods – are still necessaryand subject to future work.