What will life be like when every aspect of your existence is as easy to access as the latest Lady Gaga single? 

We treat even our most mundane lunches as if they were corpses at a crime scene. We photograph them from every angle, update friends, family, and intimate strangers on Facebook with the most salient facts about the chipotle remoulade, then file more detailed reports at Yelp. Instead of just hollering at our TV, we share our jokes about Mitt Romney’s debate attire with the rest of the world on Twitter. We review our friends’ reviews about the latest newspaper headlines on Tumblr. All of this over-sharing helps marketers, potential bosses, and sometimes even our loved ones know us a little more intimately. But how much of the data we carpet bomb the universe with daily actually comes back to us in the form of self-knowledge? 

Sure, using the fossil records you’ve left at Flickr, blogspot.com, and various other digital tar pits, you may be able to recreate exactly how you spent, say, March 11, 2008. But think about the sort of information that might truly define you and offer a glimpse into your soul. Does the amount of money you’ve spent on Coke Zero over the last five years equal or exceed your current credit card debt? Do you spend more time complaining about how much you have to clean up after your roommate than you do cleaning up after your roommate? When is your mood consistently higher—after shopping or after church? 

When trying to answer questions like that, you may find that you have no more insight into yourself than, say, a person from 1991. Twenty years, or maybe just 20 months from now, that won’t be the case. Already, a small but growing number of people are using a small but growing number of devices and apps to meticulously monitor and record their vital signs, their moods, their locations, their physical activities, their financial transactions, in ways that go far beyond the ephemeral “likes” and lulz of online lives. In 2008, Wired co-founder Kevin Kelly and Wired contributing editor Gary Wolf noticed this trend toward self-tracking and created a website called The Quantified Self to document it. The site has since spawned meet-up groups in 23 cities around the world where individuals convene to talk about what sort of data they’re amassing on themselves, and—one imagines—to take copious notes.

To some degree, we all self-track. We step on a scale, we jot diary entries in Moleskines, we may even keep fairly comprehensive logs of the miles we cycle or run and the calories we burn in the process. But just as channel-surfing grew infinitely easier in the wake of the remote control, but then infinitely more compelling as the number of channels exploded, so goes self-tracking. The $149 Zeo Sleep Coach monitors your brain’s electrical waves while you snooze and quantifies how long you spent in the various levels of sleep. The $99 Fitbit tracks the number of steps you take each day, estimates the calories you burn, and automatically uploads this information to your computer when you get near it. The Withings Wifi Body Scale takes your weight and body-fat readings and sends them wirelessly to your computer. The company’s Smart Blood Pressure Monitor jacks into your iPhone. A start-up called Green Goose is making a set of stickers embedded with motion sensors that will allow you to track how often you brush your teeth, how many times a day you open the refrigerator door, etc. The website trackyourhappiness.org sends you questionnaires via email three times each day to determine your mood. A company called Affectiva is working on a wristband that measures “emotional arousal.”

What will life be like when every quantifiable aspect of your existence is as easy to access as the latest Lady Gaga single? Traditionally, our faulty perceptions and memories have had their own kind of utility. Forgetting is the highest form of forgiving, and our inability to pinpoint exactly how we deploy our energies and resources allows us to live comfortably in the face of our own mediocrity. We may never achieve quite what we want to achieve, but at least the reasons underlying our failures aren’t constantly triggering our cellphones to send us messages telling us to shape up. In the future, when you contemplate why you’ve never quite gotten around to writing that novel, you’ll know exactly how you frittered away your life. And because we’ll be sharing much of the information we collect on ourselves, you’ll also know that it took Stephen King exactly as many minutes to write his latest novel as you spent playing Angry Birds over the last three years.

But if “self knowledge through numbers,” which is how Kevin Kelly and Gary Wolf characterize the ultimate ends of self-tracking, sounds painful, it offers some hope as well. While some self-trackers merely seek to understand themselves more accurately, a great number have tangible self-improvement in mind. Some want to use their time more productively. Others aim to cure maladies such as migraines by methodically documenting the conditions when flare-ups arise and when they don’t.

In this respect, self-tracking has a natural affinity with choice architecture, the notion that product designers or governments or other entities that shape our world can design it in ways that make it easier for us to make good choices. The more we scrutinize our behavior, the more likely we are to discern where prompts and reminders might best steer us in the directions we desire. For example, the Fitbit device can send a message to your cellphone if the day is coming to an end and you have yet to reach your daily steps goal. Our bathroom scales will eventually start calling out to us if we go too many days without stepping on them. Green Goose envisions turning various virtuous activities you might pursue—cycling to work, walking the dog, etc.—into games where you compete against family and friends to see who can amass the most points.

In this vision, individuals turn the traditional notion of surveillance on its head: By intimately monitoring themselves, they increase control over their own lives, liberate themselves from unwanted habits, pursue their goals with maximum insight—and thus better their chances of success. 

An even more profound impact may be coming on the way companies end up marketing their products and services. While consumer advocates and privacy advocates already worry that we’re offering too much information to global mega-corporations looking for new ways to exploit our weaknesses, self-tracking may not end up working quite as anticipated. 

In the Internet age, power has already shifted massively from producers to consumers, thanks to the ability to critique and compare purchases on sites like Amazon and Yelp. Right now, however, we tend to base our assessments on qualitative perceptions—the food was delicious, the plumber was punctual and seemed to know what he was talking about, etc. But imagine when restaurant reviews start to incorporate the kind of information self-trackers are beginning to keep. Soon, we’ll know if the sea urchin panna cotta at the French Laundry inspires a greater leap in heart rate than the quail egg with caviar and cedar smoke at The Ritz-Carlton. We’ll know which yoga teacher’s students sleep most soundly at night. We’ll know which activity is most likely to lead to sex on a first date—an art gallery opening or a night at the bowling alley.  

Suddenly, all the old measures that have been used to determine value and satisfaction will no longer be quite as relevant. They’ll still matter—offering a good deal and a pleasant experience will presumably lead to better experiences for customers and thus better stats from self-trackers. But the criteria used to assess and select products and services won’t be based on intellectual perceptions, which can be readily influenced by external forces. Branding, marketing, and even qualitative customer reviews will give way to reports based on blood pressure rates, galvanic skin response, and quantified self-esteem. Instead of thinking with our flighty, emotional, easy-to-manipulate brains, we’ll be feeling with our rational, measurable, hard-to-manipulate guts, crowning victors and condemning also-rans to failure based on what truly satisfies us most. Formerly intrusive marketers will run from us screaming, eyes shut, hands covering their ears, longing for the days when they had no idea what makes us tick.

Contributing Editor Greg Beato writes from San Francisco.