Consumer electronic equipments are becoming small, portable devices that provide users with a wide range of functionality, from communication to music playing. The battery technology and the power consumption of the device limit the size, weight and autonomous lifetime. One promising alternative to batteries (and fuel cells, that must be refueled as well) is to use the parasitic energy dissipated in the movement of the wearer of the device to power it. We analyze in this work the current state-of-the-art and the future prospect of energy conversion from mechanical movement in the human environment to electrical energy based upon the piezoelectric effect. This is an interdisciplinary field where material technology and electrical circuits have to advance together to improve the conversion efficiency in order to reach the energy demands of the typical portable consumer electronic devices that will become in this way autonomous wearable devices.