Disclaimer: I'm going to reference a product I built.

The science of sleep is a strange thing. Sleep is ubiquitous (after all, everyone needs to sleep), and almost everyone I know complains of being tired, or constantly groggy, or stressed due to the limited amount of sleep that they get every night. I know this particularly well, because I suffer from mild insomnia that keeps me awake far later than I should be. I try to use this time well, to create projects, or to learn new things, or to read books, but after a certain time in the night, one's brain starts to become mostly useless -- knowledge isn't retained.

All of that is background for an experience I had in late 2010. As usual, I had been sleeping badly -- getting about 4.5 hours of solid sleep per night for several weeks -- and was feeling pretty terrible, as you might imagine. That night, however, and for whatever reason, I slept beautifully for eight hours... but when my alarm clock went off, I felt terrible. I felt worse than I'd felt on four and a half hours' sleep. How was this possible?

It really bothered me, especially because I'd been so happy that I finally slept a "normal" night's sleep. Did I have some other sleep disorder, maybe one that produced insomnia as just a symptom? I researched, and tried to figure out what was really happening. I couldn't stand the grogginess I felt every morning.

During my research, which lasted probably about a month, I realized that something that made a major impact on me was the stage of sleep during which I woke up. Since sleep cycles last about 90 minutes, I felt better waking up between cycles (4.5 hours is about 3 complete cycles) than waking up in the middle of a sleep cycle (8 hours is 5.3 cycles). It turned out that this phenomenon was called "sleep inertia."

For awhile, I'd try to time this myself. I'd take a piece of paper, and count backwards from the time I needed to wake up in between cycles, then add on some time to fall asleep. I started to notice incredibly less grogginess in the morning. My new technique was amazing.

I tried sharing it with some of my friends and colleagues whom I knew also had problems getting up in the morning (who doesn't?), but it turns out that doing even simple math (subtraction) was not an activity people wanted to do right before bed. I'm not a math guy myself, so I couldn't really blame them. The timing happened to work out that I was teaching myself jQuery at the time, so I figured I'd create a little webapp for myself and my friends to use. That's how http://sleepyti.me was born.

In November 2010, when Sleepyti.me first launched, I asked HN and later Reddit's /r/programming for advice related to design and usability -- I am not a web design guy. That helped, but I ended up keeping the minimalist design in place. This choice was partially because I think it looks nice and clean, and partially because I'm not very good at design... at all. Anything more complicated and it probably would have looked terrible, knowing my design skills.

The site, much to my surprise, caught on very quickly. Social networks (Twitter & StumbleUpon, mostly) as well as traditional media found it effective and intriguing. I ended up giving several interviews about the site, being featured in LifeHacker, and being overall far more popular than I'd ever imagined. For example, I received 300,912 visits to the site last week.

I don't allow donations, and I haven't released an official mobile app yet, but the single banner page on the site has done very well for me -- I've earned $1500-$2000 per month since early 2011. It's not a startup by any means, but it's certainly a nice way to bring in some extra income from a side project.

I think the point I'm trying to make is that the article is right: the science of sleep is strange, and at times counter-intuitive... but in my opinion, it's also an untapped market. After all, we all just want a good night's sleep, don't we?