These apps will work on both the IPhone and the Android. For tracking your calorie intake there is My Fitness Pal. You can log on by phone or internet. What I like about this app is that you can add your own recipes. So there is no need to make separate meals for just you . It also has the largest "out to dinner" menu out there. So you will also be able to count your calories even when dinning out.
But of course with dieting you should also be exercising! There are a few apps out there that I think are great! The 1st one is Runtastic. I love this app because you can sync it right to your My Fitness Pal account! How easy it that....no need to remember to added anything. Life is hard enough and here is one less step you need to do.
The 2nd app is MapMyRun. This app, I think is the MyFitnessPal and Runtastic in one! This app allows you to map your route, log your food and track your activity all in one. Don't want to start an account, you can log in with both facebook and twitter. So find a friend or your partner for support.
3rd and finale app is RunKeeper. This app is just to track your work out. So if your not looking to track your calories or log your food intake for the day then this app is for you. This is just a simple way to track your runs.
I hope what you decided to use to help you loose weigh you do it safely! I don't want any brides passing out on the day of their wedding.