Lawn Bowls app developer for Andriod and ios phones. Distance measure/comparing

In lawn bowls there is a definite need to be able to judge with precision which bowl is nearest the Jack at the end to determine the score. (the Jack is a small white ball rolled first and then players take turns to try get 1 or more of his 4 bowls closest to it). Bowls is generally and older persons sport, and judging minute distance from the jack can be tricky. conventional methods employ tape measures and cumbersome gadgets to try get between the bowls. This app will judge the nearest to the jack from the smart phones camera. The user will have to place the camera directly over the jack and let the app do its job. There are regulations for size of this jack (must be no less than 63mm and no more than 64mm) and that may help in the developing of the app. App must be large print, easy to operate, as few steps or buttons as necessary, and have a clean interface to be older person friendly.