In five years fitness trackers probably won't be a thing. They'll be built into watches or clothing or your phone. But right now they come in all shapes and sizes and they're the best way we have to use technology to get in shape. There are a million of them and they all do essentially the same things. They count your steps and they tell you if today's number is better than yesterday's. But a really good one will also tell you if you're not sleeping well. It will remind you subtly or not so subtly to eat better or go to bed a little earlier or get out and exercise more. And it either looks good or is basically invisible, or both.