The iPhone, because of its fits-in-your-pocket size and because of its GPS, is great for tracking your fitness, whether it's what you eat or what you burn. I use RunKeeper, and sometimes Zombies, Run! to track my walking (or my rare and brief running). However, I use Lose It! To track my food intake and my exercise, to try to stay in a calorie budget and lose weight.
That's a number of apps with redundant information in them. Much of my exercise gets recorded in either RunKeeper or Zombies, Run! And also gets recorded in Lose It! I hate entering the same thing twice. you probably do too. If you have an account with each of the services behind these apps, however, you start RunKeeper or Zombies, Run! and have your caloric expenditure automatically show up in Lose It!
Here's how I have it set up:
And here's how to do it:
Happy syncing!