Future wearable technologies and personal electronics can be benefit from e-textiles that simultaneously possess high elasticity and multiple capabilities such as energy harvesting and sensing. In this talk, we will present an intrinsically stretchable liquid-metal nanogenerator fiber that can harvest both mechanical energy (e.g. from the body) and electromagnetic energy (e.g. from nearby electronics such as laptops, cell phones, transformers). Furthermore, to the best of our knowledge, this is the first single energy-harvesting fiber that simultaneously possesses inherent elasticity and extraordinary stretchability with the ability to harvest two sources of energy (that are mechanical and electromagnetic Energy). This is also the first report of fibers that convert dielectric-loss from electronic devices to electricity. In addition to converting multiple sources of waste energy into electricity, the fibers can act as self-powered tactile and biomechanical sensors. The fibers consist of hollow elastomeric fiber filled with liquid metal. The fibers harvest energy by the combination of triboelectricity (160 V/m, 5 μA/m, and ~360 μW/m) and induced electrification of the liquid metal (8 V/m (60 Hz), 1.4 μA/m, and ~8 μW/m). We characterize the fibers and demonstrate their utility for powering electronics and sensing biomechanical information. These fibers are further demonstrated as completely soft and stretchable components for human-machine interfaces, including keypads and wireless music controllers. The findings of this work provide new advancements in stretchable/wearable energy and sensing technologies, which are both timely and could advance a wide range of emerging wearable technologies and personal electronics.