From All About Circuits: Google ATAP is bringing touchless interfaces to the market using a miniaturized radar chip no bigger than a dime. This is Project Soli.
Soli’s radar sensor is a marvel in many respects. For one thing, it solves a long-lived issue when it comes to gesture-recognition technology. Previous forays into the topic yielded almost-answers such as stereo cameras (which have difficulty understanding the overlap of fingers, e.g.) and capacitive touch sensing(which struggles to interpret motion in a 3D context).
Google ATAP’s answer is radar.
Radar is capable of interpreting objects’ position and motion even through other objects, making it perfect for developing a sensor that can be embedded in different kinds of devices like smartphones... (full article)
The ST Robotics Workspace Sentry robot and area safety system are based on a small module that sends an infrared beam across the workspace. If the user puts his hand (or any other object) in the workspace, the robot stops using programmable emergency deceleration. Each module has three beams at different angles and the distance a beam reaches is adjustable. Two or more modules can be daisy chained to watch a wider area. "A robot that is tuned to stop on impact may not be safe. Robots where the trip torque can be set at low thresholds are too slow for any practical industrial application. The best system is where the work area has proximity detectors so the robot stops before impact and that is the approach ST Robotics has taken," states President and CEO of ST Robotics David Sands.