In order to increase the power autonomy of implantable sensors, energy harvesters can aid and, in certain cases, substitute implantable batteries. The paper describes two promising techniques among the approaches presented in literature: biofuel cells and inductive powering. For both tech- niques, key points and drawbacks are illustrated, together with a summary of the solutions pre- sented in literature. Potential methods to enhance the performance of biofuel cells by means of nanostructured materials are presented and discussed.