The story of SunSprite begins, of all places, on a road trip. It was the summer of 2011, and we were finally on vacation. The countryside was gorgeous. The weather was spectacular— brilliant sun alternating with torrential rains. Yet those magnificent surroundings could not distract us from worrying about our patients (we’re Harvard psychiatrists). Or keep us from thinking about what we wanted to do next. Friends and colleagues assumed we were writing another book together, but we didn’t want to. We wanted to do something different.

Just before we left on our trip, we read an article in The New York Review of Books by Marcia Angell, the former editor of The New England Journal of Medicine. Her review of three new books on psychopharmacology described the disillusionment patients and doctors feel with many psychiatric drugs. Dr. Angell’s eloquent article captured a sentiment we shared: dismay that the side effects of some of these medicines were as bad as the illnesses they were trying to cure.

We found ourselves wishing that we could do something else to help people feel better. Something without the side effects of medication, and something more direct than writing another book.

As we travelled, we kept noticing the light.

Both of us had prescribed bright light therapy for people with depression for years. It works for seasonal depression (SAD). It works for non-seasonal depression. It helps people without any clinical depression improve their mood, alertness and vitality. We were using light therapy as far back as the late 1980s, when the first studies of its effectiveness were published, commercial light boxes (lamps that emit a specific intensity of light) were not yet available, and we sent patients to their local hardware store with a shopping list of parts to build their own. Since then, dozens of medical studies have repeatedly proven that bright light therapy is just as effective as many psychiatric medications, but without side effects.

The science is (almost) straightforward: light is our body’s time-giver (or “zeitgeber,” as it’s called in most scientific articles). When light enters the eyes, it stimulates specialized receptor cells in the retina that have connections to the brain’s hypothalamus, specifically to the suprachiasmatic nucleus—the “master pacemaker” for our circadian rhythm.

Without bright light, a person’s internal rhythm falls out of sync with the external rhythms of their daily life. What can follow is depression, apathy, or the muddled feeling of jet lag without ever having left home. A recent New Yorker article called this “social jet lag”.

We knew these facts. And yet we struggled to effectively harness bright light’s benefits for our patients. People rarely felt sure that they were doing it correctly. What could we do to make light therapy more accessible and easier to use and understand?

We imagined how terrific it would be if people could be free to live their lives while also getting the proper amount of light. They could go outdoors for a walk, or drive their car with the light streaming through their windshield, or sit by a window while reading a book or listening to music. If there were some kind of personal light meter to measure the amount of light a person was exposed to in various settings, then no one would have to disrupt their life because of a lack of options: a light box would become only one among many possible sources of beneficial light.

We wanted to find a way for a person to get 10 minutes of light at the breakfast table with their light box, and then get the next 20 minutes in the sunshine on their way to the bus stop, and still know that they had gotten the right amount. Or they could get their whole 30 minutes of light in the sunshine and skip the light box entirely. This just seemed like a much more practical and comfortable way for a person to use light therapy.

Why not simply go outside more often or spend indoor time more frequently near windows? Such changes could be helpful, but the key is understanding that the light must be bright light in order to work properly and benefit your health—and a person needs to know when the light is bright enough. The difficulty lies in identifying the level of brightness: human eyes are great at adapting to contrasts in light, but they need help accurately measuring light intensity.

The personal light meter we imagined would be able to precisely measure light intensity and aggregate these measurements over time, calculating the day’s total and enabling the person to quantify their exposure—thereby helping the person to ensure that he or she was making the healthiest choices.

The world is filled with pedometers and (in the world of scientific research) radiation badges. We thought we could combine those two models and create a new type of wearable tracker. And watching the growing disillusionment with medications, we thought many people would be looking to return to more natural ways of improving mood, energy, focus, and sleep.

As we worked out our specifications for this personal light meter—which we would soon name SunSprite—we developed a growing awareness of the far-reaching effects of light on everyone, not only on our patients; after all, any person can attest to how much difference a sunny day makes.

Plus, modern technology increasingly confines people to the artificial glare of their computers, televisions, tablets, and smartphones. Emerging scientific evidence points to the unhealthy disruption of circadian rhythm that such 24/7 exposure can have on a person’s health—particularly on their quality of sleep, not to mention their energy level, ability to focus, and overall mood.

What began as a useful measuring tool for our patients quickly became something greater: a personal light coach for anyone and everyone seeking to improve their overall wellness and maintain their health at the highest possible level.

Our enthusiasm for this idea soared as we realized that SunSprite could help countless people across the country and perhaps even around the world. As doctors, we dedicate ourselves to helping the patients who arrive on our doorstep. We cherish each of our patients and the healing work we do together.

So we were appropriately humbled by the potential of SunSprite to touch the lives of people who want to live brighter lives, people whom we may never meet. SunSprite could empower every individual seeking to become their brightest self. It could serve as a trusted sidekick whose suggestions would be built on proven scientific fact.

As we prepare to launch our first version of SunSprite, we hold in our minds the knowledge of light’s natural effectiveness and in our hearts the hope of helping people to become their brightest selves. You might say that we’ve seen the light—and we hope you will too, with SunSprite.