I have been carrying my Fitbit One for a little over two years with me and it keeps tracking my daily steps. It also tracks my distance covered by multiplying those steps using the stride length which you can either provide explicitly or implicitly setting your heights. In the winter of 2012 I bought my first ~Garmin Forerunner 410~ (replaced by a Garmin Forerunner 920XT) GPS watch to help me track my running (and other outdoor) activities.
One of the most important features in quantified self is the ability to export your data in an open format. Fitbit lets you download your personal data if you subscribe to a premium membership. Alternatively they provide an API at dev.fitbit.com/ that allows developers to interact with Fitbit data in their own applications, products and services. In a blog post at quantifiedself.com Mark Levitt shows a way how to export your Fitbit data into Google Spreadsheets.