Hi nessa - yes there are lots of different ones out there, diabetes uk have a free one, I'm personally a fan of the mySugr app which is free for a basic version, I have chosen to pay for the upgrade which gives you a lot of additional features. Search for diabetes in the app store and you will see plenty of options, just choose one that you think is right for you - I always think something that makes you WANT to use it is best because it makes tracking your BG levels an easy habit to keep.
In terms of Carb counting there is the carbs and cals app, also a lot of people use my fitness pal.