There are more than 165,000 apps to track your health and fitness available. Of these only 36 apps account to more than 50% of downloads according to a study by IMS Institute for Healthcare Informatics which analyzed 26,000 apps.
Interestingly, only 10% can connect to a device or a sensor and only 2% sync with any providers systems.
I have been tracking my steps, calories burnt and fitness (Running and Training) very sincerely for over 2 years and have been tracking my food off and on.
There are a variety of apps available and my recommendation would be to try few before you finalize on what you wish to use.
It will be interesting and exciting to be using and tracking activities in various apps, but over the period of time it will become monotonous and you will start to be away from them.
Which apps to select?
First, identify your goals (Food, Steps, Calories, Running, Walking, Swimming, Cycling and workouts). Then look for apps which provide you with the information you wish to track and the ease of use and then finally settle down on what you wish to use.
I personally use a Garmin Vivofit, so I use the Garmin iOS app. Over the period of time, I also bought a Triathlon watch (Garmin Forerunning 920) and hence it became more easier to track all my activities. For food, I use MyFitnessPal which integrates with Garmin App.
In summary, use the apps which motivate you and your data syncs to the servers instead on being remote on your device.