This disclosure provides systems, methods and apparatus for wireless data communication. In one aspect, a device communicates with a base station. The device comprises a circuit configured to generate energy based on an environmental input. The device further comprises a storage device configured to store the energy. The device further comprises a clock circuit configured to generate a clock signal. The clock circuit is configured to power on during an active state of the device and power off during a sleep state of the device. The device further comprises a trigger circuit configured to generate a trigger signal that transitions the device into the active state when a level of the energy stored reaches a threshold value. The device further comprises a transmitter configured to transmit a message to the base station in response to generation of the trigger signal.