Energy efficiency will play a crucial role in future communication systems and has become a main design target for all 5G radio access networks. The high operational costs and impossibility of replacing or recharging wireless device batteries in multiple scenarios, such as wireless medical sensors inside the human body, call for a new technology by which wireless devices can harvest energy from the environment via capturing ambient RF signals. SWIPT has emerged as a powerful means to address this issue. In this article, we survey the current architectures and enabling technologies for SWIPT and identify technical challenges to implement SWIPT. Following an overview of enabling technologies for SWIPT and SWIPT-assisted wireless systems, we showcase a novel SWIPT-supported power allocation mechanism for D2D communications to illustrate the importance of the application of SWIPT. As an ending note, we point out some future research directions to encourage and motivate more research efforts on SWIPT.