This document discusses quantified self apps that allow users to track various aspects of their lives for self-improvement purposes. It outlines apps for tracking diet, exercise, mood, sleep, productivity, and overall health. These apps allow users to collect personal data, see patterns emerge over time, and potentially use the data for purposes like personalized medicine, workplace wellness programs, education, and more. However, the document also notes privacy and data sharing are concerns with these types of highly personal tracking apps.