I'm in the middle of testing the BodyMedia Fit Armband, which tracks your calorie burn, steps, exercise times, and food intake in order to help you drop pounds smartly.
Wearing the band for up to 23 hours a day, you can program how much weight you want to lose and how quickly. Insert your stats (like body weight, height, and how often you normally work out), and BodyMedia will come up with goals for you to hit each day based on your BMI, calorie intake, and activity level. You can see all of your daily results in graph form, which makes it super easy to tell where you need to work harder, and you won't have to do any crazy math to figure out your calorie deficits — it's all done for you! Best part — the BodyMedia Fit Armband connects with your iPhone over Bluetooth and the BodyMedia app, so you can update your stats on the fly.