This review explores the current state-of-the-art wireless and mobile optical chemical sensors and biosensors. The review is organised into three sections, each of which investigates a major class of wireless and/or mobile optical chemical sensor: (i) optical sensors integrated with a radio transmitter/transceiver, (ii) wearable optical sensors, and (iii) smartphone camera-based sensors. In each section, the specific challenges and trade-offs surrounding the (bio)chemical sensing mechanism and material architecture, miniaturisation, integration, power requirements, readout, and sensitivity are explored with detailed examples of sensor systems from the literature. The analysis of 77 original research articles published between 2007 and 2017 reveals that healthcare and medicine, environmental monitoring, food quality, and sport and fitness are the target markets for wireless and mobile optical chemical sensor systems. In particular, the current trend for personal fitness tracking is driving research into novel colourimetric wearable sensors with smartphone readout. We conclude that despite the challenges, mobile and wearable optical chemical sensor systems are set to play a major role in the sensor Internet of Things.