Wearable haptic technologies, known as wearable haptics, instantiate physical contacts with users, either to confirm actions or to communicate a surrounding information-over a worn-type interface. Two factors require to be addressed for their design: the body locus-a function of comfort and sensitivity, and the types of stimuli they provide. Wearable haptics have gained great popularity in the last decade, thanks to their effectiveness, ease of use, and variety of application scenarios. This paper provides a non-exhaustive review of the state of the art on wearable haptics for navigation guidance. We classify the existing literature through two dimensions: (1) the body part they stimulate and (2) the haptic stimulation they provide through their actuation technology. We then analyze the navigation guidance strategies they adopt for communicating with the wearer, to finally identify challenges and limitations reflected in their evaluation protocols. Compromises are to be drawn when eliciting guidance through wearable haptics, between acceptability, cognitive workload, usability and accuracy.