This paper presents three different techniques for efficiently powering an energy-autonomous wireless sensor (EAWS) through both energy harvesting (EH) and RF wireless power transfer (WPT). The aim of the paper is to provide effective strategies and techniques to reduce, as far as possible, the cost of wiring of the automotive production process due to the continuous and constant increase in the use of sensors. The techniques employ a highly integrated state-of-the-art, ultra-low power 2.5 mu W system-on-chip (SoC) system, designed for multi-source RF wireless energy harvesting and power transfer and are designed with the goal of minimizing and, where possible, eliminating the costly maintenance required by conventional wireless sensors. Specific examples are reported that define both the aspects of convenience and the limits of use.