In this talk, I will present our work on building low-power wireless connectivity using commodity WiFi devices. An existing wireless radio consumes lots of power because the radio itself is the device which generates the wireless signal. Our key observation is that we have been surrounded by lots of wireless signals, such as WiFi. Why not reflecting existing WiFi signals and embedding our own information? We design and build practical systems to show that this is feasible and promising. Our device embeds data on top of unknown WiFi traffic by changing the codewords used by WiFi systems. We demonstrate that our system works with commodity WiFi without modifying the WiFi hardware. We also demonstrate that we can embed ECG and camera sensor data on top of existing unknown WiFi traffics. We achieved around 300 kbps data rate at close distance (~10m) and the maximum communication distance of our system is 42m in line-of-sight deployment.