An accessory strobe device for a mobile device may operate to provide illumination at the same time as an internal built-in strobe (flash) of the mobile device. The accessory strobe device may receive a single, unidirectional signal from the mobile device that provides signals related to the timing of the internal strobe. The accessory strobe device may process the received signal to control its illumination using the timing and relative intensity levels of the internal strobe during metering and main (normal) flash operations associated with a camera on the mobile device. With the accessory strobe device operating using timing and relative intensity levels in a predetermined relationship with the timing and relative intensity levels of the internal strobe, the accessory strobe device may be used to complement the internal strobe during the metering and main (normal) flash operations for the camera.