Despite the rapid growth of wearable and mobile devices and associated availability of vibrotactile (VT) actuators, the design space of VT applications has remained primarily limited to event-based VT notifications. While useful in some cases, these notifications can be disruptive and cognitively-demanding. Further, the lack of perceptually salient VT sensations on consumer-grade actuators prevents use of these notifications in information-rich scenarios. In this paper, we extend the design space of VT applications by utilizing users' touch input (e.g., 2D location, path, etc.) together with VT sensations for smartwatch interactions. We examine previous work on touch-based haptic interactions for other tactile technologies and propose a design space for VT interactions. Then, we investigate user performance (error rate, completion time, perceived demand) for touch-based VT interactions with a user study. Finally, we populate the identified design space with five example applications that run on off-the-shelf smartwatches.