If you want something done, do it yourself, the old saying goes. It’s a philosophy that fuels the “quantified self,” a growing movement toward tracking one’s life with the help of technology. It extends far beyond Nike’s (NKE) groundbreaking Nike+ running app: Devotees can dutifully track fitness routines, eating habits, even medical conditions. And companies are developing tools for nearly every scenario imaginable. Here are just a few.

Fitness

RunKeeper employs a phone’s GPS to track activities like running and cycling, and through its Health Graph lets users compare performance. Devices like the Fitbit apply a data-tracking method called actigraphy to gauge movements during sleep.

Medicine

The Spiroscout sensor, an inhaler attachment, uses satellite data to show asthmatics locations that may worsen their condition. The Boozerlyzer, built to measure blood alcohol levels, can be doctored to track drug intake and side effects.

Lifestyle

With GreenGoose’s sticker-size sensors, everyday items  — toothbrushes, toys, even pets — transmit data back to an egg-shaped base station. Users can keep track of information such as how often they’ve brushed their teeth or if someone walked the dog.

This story is from the October 8, 2012 issue of Fortune.