Abstract: A stand-alone device includes an integrated circuit (IC) die (optionally free of conventional IC packaging and bond pads) that responds to a signal by (1) storing energy retrieved from the signal, and (2) using the stored energy to generate another signal that is encoded with information provided by a data source (such as a memory or a sensor depending on the implementation) that is included in the device. The IC die includes a power supply, a signal transmitter, and optionally includes an antenna. During operation of one embodiment, the power supply receives from the antenna electrical energy extracted from a portion of a radio frequency signal incident on the IC die. The power supply stores the energy in an energy store over a period of time, and thereafter supplies at least a portion of the stored energy to the signal transmitter.