Carb manager is my very favorite. I try to eat low-carb, and the carb manager does better at tracking carbs as well as calories than my fitness pal does (unless you buy the expensive version of MFP). Carb manager also connects with my Apple Watch and adds in all of my exercise; so I have everything in one place, and it is easy to make my own recipes and then have it portioned out with how much I eat of something.
I also use a fasting tracker called “LIFE”, ad it is good at keeping track of how long I have fasted, providing I don’t forget to set it, or to turn it back off when I have my OMAD meal.