If you've got typical levels of binocular depth perception: Close one eye. Slowly poke something 2-3 feet away. You can do it, but you might be off an inch or

If you've got typical levels of binocular depth perception: Close one eye. Slowly poke something 2-3 feet away. You can do it, but you might be off an inch or two with your distance estimation and be surprised when you actually make contact. Open both eyes and do something similar with another object. The added depth information should mean that you can tell where something is to a greater precision. Same thing with Tango. In both cases, you can extract some information about the environment from a 2D image stream. Add in accelerometer, gyroscope, and depth-sensing hardware, and you can correct some of the edge cases while increasing precision even for the things that you could do with standard hardware.