I have always poo-pooed those things, but I should give that a shot.
I've counted calories before, but this makes it easy to track, no pen/paper to worry about. You can search foods, scan labels (I've found only one label that wouldn't scan so far, out of hundreds),input restaurant information, etc... Input exercise, you can even enter your own recipes (ingredients list) and track by the finished product servings. It's really pretty neat. It's My Fitness Pal by Under Armor. Free with ads, or pay for it.