In some embodiments, a personal area network (PAN) includes a mobile transmitter (e.g., a mobile or cellular phone) and one or more devices (e.g., sensors) that require power to operate (e.g., collect data). The mobile transmitter can be configured to transmit a sufficient amount of power (e.g., RF energy) to the one or more devices to power the one or more local devices. In addition to transmitting power, the mobile transmitter can be configured to communicate over a wireless network (e.g., a cellular network) as its primary function.