We've looked at a number of fitness-tracking devices like the Fitbit, Nike+ Fuelband, and Jawbone Up, and have generally found them to be useful tools for tracking your activity and motivating you to get off the couch a bit more often. Dan Hon, a writer for Domus, recently took things a bit farther — after being diagnosed with type 2 diabetes, Hon turned to the Fitbit and Nike+ Fuelband to help keep fitness top-of-mind. Hon found the experiment to be largely successful, but the longer he used the devices, the more he became aware of the "Balkanisation" of his fitness data. Read on to learn about the many benefits of tracking your activity as well as the potential pitfalls of giving your fitness data over to a single source.