Smart Measure

Smart Measure is an app that lets you calculate short distances with your Android. Just point your camera in the direction of a nearby object, and the app calculates the distance between the camera and the object.

Smart Measure is very simple to use; you just have to enter the height of the object whose distance you want to measure, and adjust the lines. This way, you can instantly measure its distance from you. For some easy references: the height of an average person is about 1.7 m (5.5 ft), a door is usually about 2 m (about 6.5 ft), and a chair is usually no more than 1 m (3.28 ft).

The 'pro' version of the app lets you access additional features. With it, you can measure the width of objects and use the camera's zoom.

Smart Measure is one of those apps that seems almost magical. Unfortunately, it's not magic, it's just math.