Intelligent tires are one key element for autonomous self-driving cars and the Internet of Vehicles (IoV), especially if the battery-driven sensor systems attain the transition to be self-powered. Harvesting vibrational energy of these tire pressure monitoring systems (TPMSs) is the promising technique to make tire sensors self-sufficient and to provide additional energy for sophisticated algorithms, which constitute the intelligence of vehicle tires. Despite of two decades of intense research, no commercial product has been established. This work analyzes the technological reasons and presents both challenges and opportunities of TPMS energy transducers. First, this article specifies significant system requirements and characterizes common energy sources. The authors determine the necessary amount of energy on two different paths. A throughout comparison between different TPMS transducers overviews the state of the art, comprehensively. Typical TPMS energy harvesters are summarized, distinctive TPMS transducers are shortly presented and common problems are outlined, focusing on the harvesting mechanism, restoring force, interface circuit, and energy generation. The pros and cons of different energy transducer principles for their operation inside the tire are balanced. Focusing on reliability and on normalized energy generation, this publication highlights potent energy harvesters for system enhancement and gives recommendations for future developments. Two significant outcomes among others are to switch the focus from linear systems to systems with a nonlinear restoring force as well as to more efficient interface circuits than low-efficient full-wave rectifiers.