A wireless system including an antenna, an electrical energy storage unit connected to the antenna, the energy storage unit receiving power via electromagnetic coupling of the antenna with an RF field generated by a master unit, and an electronics package. The electronics package is powered by the energy storage unit, and it includes a sensor, a processor that is capable of acquiring data from the sensor, and a transmitter connected to the processor and to the antenna, wherein the energy storage unit is capable of storing sufficient energy to supply power for the processor to format a message containing data acquired from the sensor and for the transmitter to transmit the message wirelessly via the antenna.