Among the available solutions to harvest energy from vibrating and non-vibrating sources, piezoelectric bimorphs seem to be a suitable choice due to their capability to directly convert applied strain energy into usable electric power. This work reviews the techniques adopted to increase the specific power per unit of volume of piezoelectric scavengers. The design goal is to obtain a uniform stress distribution on the piezoelectric layers, in order to exploit the electro-mechanic energy conversion capability of the whole material. Two approaches are then followed to improve the performance: by designing an optimal shape of the device, or by imposing an optimal bending deflection. For both strategies, results from numerical models and experimental tests are compared.