I've tried a few but prefer DiabetesDiary. Also has a separate app called InsulinCalculator which sends results to it if needed. Both paid for apps but worth it IMHO.
I use cals and carbs, I find it really useful. I also use diabetes plus, which I think is brilliant, you record BG. Insulin taken and carbs consumed, it gives you your statistics and you can print or email them, useful at check up time.