With the first Android 11 developer preview out, more and more upcoming features are beginning to surface. The latest one is a new double-tap gesture that is performed on the back of the device and triggers the Google Assistant by default but can also be changed to open the camera app. The new feature is codenamed Columbus and is seemingly going to be exclusive to Google's Pixel line initially. The way it works is still a mystery but it appears to be picking up the knock on the back via the accelerometer or gyroscope sensors so it doesn't require special hardware to function. It...