Strobox

Strobox App is a lighting diagram creator for your iPhone or iTouch. Whether you want to repeat the same photo-shoot or share with others how you made that cool shot, Strobox app will give you the right tools to do so. It generates PNG files that you can share with anyone by sending it by email within the app.
The app gives you over 25 lighting equipment choices, backdrops, strobes, softboxes, umbrellas, hairlights and diffusion panels. Link