A wireless power receiver includes a rectifier coupled to an antenna which is configured to receive a wireless power signal, and convert the wireless power signal to a direct current input signal. A direct current-to-direct current converter generates a direct current output signal based in part on the direct current input signal and a pulse-width modulation signal. A pulse modulator is configured to adjust an alternating current impedance of the wireless power receiver by modifying, based in part on the direct current input signal, a duty cycle of the pulse-width modulation signal to the direct current-to-direct current converter. A monitoring device is in communication with the rectifier and the pulse modulator. The monitoring device has one or more sensors and a unique user ID. The one or more sensors acquire user information selected from of at least one of, a user's activities, behaviors and habit information.