This is an article in Wired about parents who track everything about their kid, because with modern technology, they can. I'm sympathetic to this. When you have a kid, it becomes your hobby. (At least, it became ours.) It's what you and your partner do in the evening, sit around and watch the kid and talk about it. Less so with later ones, but the first one is enthralling.
And if you're a data geek and a technology freak (like the economists in the article, on both counts), why not use technology to keep track of stuff? There may, for all one knows, be some use for it later on, but for a real data geek, keep track of something is its own reward, and I sympathize greatly with the affliction.
So now that you can, for example, use an iPhone app to enter data on when the kid sleeps, wakes, poops, or cries, and some toys record how they are played with, we can each be our own Darwin, observing our kids just for the hell of it.
The Wired article has some links to devices and software you can purchase.