This article reviews some recent promising approaches to make mobile power closer to reality. In contrast with articles commonly published by the microwave community and the communication/signal processing community that separately emphasize RF, circuit and antenna solutions for WPT on one hand and communications, signal and system designs for WPT on the other hand, this review article uniquely bridges RF, signal and system designs in order to bring those communities closer to each other and get a better understanding of the fundamental building blocks of an efficient WPT network architecture. We start by reviewing the engineering requirements and design challenges of making mobile power a reality. We then review the state-of-the-art in a wide range of areas spanning sensors and devices, RF design for wireless power and wireless communications. We identify their limitations and make critical observations before providing some fresh new look and promising avenues on signal and system designs for WPT.