I have produced an app to teach users how to communicate using Navy Flag Semaphores. The UI was built with UIKit.

For getting the camera input, I used AVFoundation. I used VisionKit to produce a list of arms points from the camera input. These points are then mathematically processed to calculate the represented flag (don't worry, you don't need to hold a flag).

The app has two modes, learn and game. Learn will show you the flag you must represent and its corresponding letter. This is ideal for users who have never seen this before and need to get to grips with it.

The game mode only gives the user the letter they should be showing. The aim is to get as many points as possible in 60 seconds. A point is scored by correctly representing a flag.

On the right side of the screen is the camera display, with the points seen by VisionKit marked on. If no points are displayed, try adjusting your lighting. I found the best place to leave my iPad was on a chair and then took five steps back. Before starting each mode, a calibration phase will happen to ensure that the camera can see you at all times. I suggest not wearing any baggy clothes as this can obscure the readings.