This may sound contrarian, but the engineering tech in a fitbit isn't what it's cracked up to be. Many of the cool kids wear them, and it gives you a rough Idea of what your sleep patterns, steps, and heart rate are. However, they aren't terribly accurate. In essence, it's a glorified 20 dollar pedometer which can be fooled by shaking it for 2 minutes to get your 10000 steps in for the day. Your money is better spent on other devices.
Chest strap HR monitors like the Wahoo Tickr X are far more accurate for tracking your activity during exercise.
myfitnesspal is a very good app to track your eating habits. Losing weight is 85% watching your diet. Exercise is great for your body, and stress, but you need a good diet of balanced macros to lose the weight. Then, you need a second diet to live with once you've lost the weight, or it'll all come back. Good luck to you.