Do you find Self Tracking useful like Stephen Wolfram does?

Manzanita writes: "The domain of personal analytics, or "Quantified Self" is rich with interesting things to measure and many hackers have started projects. But they will only take off if it is sufficiently easy to gather and use the data. Stephen Wolfram has collected and analyzed a lot of his personal data over the last 20 years, but that is far beyond what most of us have the time for. What do you find worth tracking? What is ripe for developing into a business? http://blog.stephenwolfram.com/2012/03/the-personal-analytics-of-my-life/"