Try Linear Technology - http://www.linear.com/parametric/Energy_Harvesting for Piezoelectric, solar and magnetic energy harvesting ICs. ST, TI, and MicroChip all make evaluation kits for energy harvesting (mainly solar).
In order to our RF energy harvesting experiments, these ICs (Linear Tech.) not suitable on Rf harvesting application because of their input impedance value. But, in application notes they are suitable option for other harvesting technology such as vibration, TEG and so on.