I have been looking to buy a light meter since I have been shooting more film . At the same time some light meters can cost the same as a lens and it isn't something I will be using everyday. I stumbled across the Luxi kickstarter project and my problems were solved.
There are some disadvtanges, the attachment doesn't have a pc sync port to trigger lights for metering. I am still impressed by the price and have backed the project myself. Check out the kickstarter video below for more information and see if you would like to be a backer. Prices are at $19 for an iphone 5 and 4 setup. Luxi Kickstarter