AccuLevel it's a reality augmentation app to measure angles, test the alignment of structures and know if something its horizontal or vertical with your camera.
You only need to align a reference line on your display with the camera image, the tilt sensors will do the rest to get the angle.
The app its touch customizable. You can zoom in and out of the displayed scene, change the reference line orientation from horizontal to vertical or its position with a press of a finger.
Caution: You must avoid parallax errors. They appear when the camera isn't properly aligned with the objects to measure. To minimize them align the horizontal indicators on the border of the display with the horizon and place the camera on the same horizontal plane as the object.