This paper proposes a compact time-sharing solution for energy harvesting and vibration sensing by making full use of a modified buck-boost design. Compared with the other self-powered synchronized switch PEH solutions, which rely on analog peak detectors, this self-sensing solution not only provides synchronized triggering signals for carrying out the switching actions but also tells more information about the driven vibration, such as its frequency and displacement magnitude. With the detailed vibration information, such a time-sharing solution offers more design convenience towards future multi-functional battery-free IoT applications.