I personally use the sparkpeople calorie counting app, don't really know why. first one i came across and stuck with it.
Honestly, I've been battling being overwieght for a LONG time, and I just strted a new lifestyle and i myself want to shed a lot of weight. But from the amount I've done so far, this app has been a lifesaver. I never understood portion control or portion sizes. And i never really realised how much I put in my mouth everyday.
I've gone as far as measuring the tablespoon of ketchup im about to consume. I scan barcodes like crazy and learn so much about food. it has been the one thing thats kept me motivated and confident that I can do this. I used to keep a food journal but all that did was track what i ate and possibly the calories. Now I have a restriction and scale of proteins, carbs and fat. As well as water and exercise.
From my small experience, an app to count whatever you are counting (calories, carbs, fats, protiens ANYTHING). is going to be huge.
Just my honest opinion.
Good luck on your weightloss