See through walls with android smartphone attachment

There is an $85 android smartphone add-on device that lets you clearly image through up to 4 inches of concrete wall.

Walabot is a 3D RF imaging sensor. The 3D imaging is created using radio frequency technology, the same technique we use for Wi-Fi, mobile networks, and radar systems. Antennas in the Walabot firing out signals and sensors to pick up the reflections.