SleepCycle: The Smart iPhone Alarm Clock

I’m not an insomniac. Not really. I just picked up an unfortunate habit in college of not getting to sleep until 3am, and I haven’t quite managed to get rid of it yet. Partly as a result, I’ve been wishing vaguely for a FitBit for some time now. $100 is a bit much to spend just to feel guilty for not exercising enough, though, so I haven’t acquired one yet.

Then a friend told me about Sleep Cycle, an app that claims to track your sleep patterns and wake you at the optimum moment in your sleep cycle, resulting in a more natural and restful awakening. At $.99, testing it was a no-brainer. Here’s what I found.


Sleep Cycle uses the accelerometer in the iPhone to track your movement as you sleep, so it needs to be on your bed to get anything approaching useful results. Since the app can’t run in the background or when the screen’s locked, it’s best to leave the iPhone charging. A charging, running iPhone can get hot if it’s covered—and sometimes even if it’s not—so it’s important not to accidentally stifle your iPhone with a heavy blanket or pillow.

Placing Your iPhone

Placing Your iPhone

Once you’re confident that you won’t drain your iPhone’s battery overnight or cause it to burst into flame, setting your iPhone up for the night is pretty straight forward: set your alarm in the ‘Alarm’ tab, read the helpful reminders, and place the iPhone face down on your bed. Simple and done.

Set Up Your Phone

Set Up Your Phone

How It Works

A momentary digression into science: there are two main kind of sleep, rapid eye movement (REM) sleep and non-rapid eye movement sleep. In REM sleep, which is when most memorable dreams occur, the eyes move rapidly—surprise—but the rest of the body is effectively paralyzed by a phenomenon known as “REM atonia”. Without getting into the details, this means that the body is generally still during REM sleep. In NREM sleep, dreaming is rare and the muscles aren’t paralyzed.

Comparing this information to the graphs produced by Sleep Cycle suggests that the “Dreaming” level of the graph is probably mislabeled. That movement level probably represented NREM sleep, while the lower levels of moment should represent REM sleep and the accompanying paralysis.

While Sleep Cycle is good for getting you up at the right time to minmize grogginess, if you insist on gettng a small amount of sleep, there’s only so much Sleep Cycle can do to help you. In apparent recognition of that fact, the app refuses to even track amounts of sleep less than three hours, so don’t try to use it to track a nap.

Since being awakened from REM sleep often results in grogginess, Sleep Cycle should try to wake you at the most movement-intensive part of the thirty minute window preceeding your set alarm time, and in my experience it does exactly that.

The alarm can be one of several built-in sounds; in accordance with Sleep Cycle’s goal of a relaxed, natural awakening, the sounds it uses are in general much less jarring than those used by the iPhone’s built-in alarm clock.

Analysing Results

Analysing Results

What You Can Do With It

If you’re curious, you can track your past nights’ sleep in the Statistics panel. This is especially helpful if, like me, you find that the positive reinforcement of well-formed graph encourages you to keep up a normal sleeping pattern.

You can also email your graphs to someone else, which might be especially useful for those tracking a sleep disorder under the supervision of a doctor, or even share your sleep graphs on Facebook (if that’s your thing!)

Final Thoughts

There are several competitors in the App Store. Sleep Phase Wakeup Clock by Tuomas Artmen also offers the ability to track your sleep patterns with the microphone instead of just the accelerometer, but comes packaged with an icon that seems to include a reversed but otherwise identical version of the arrow/clock from the Time Machine icon.

The Absalt alarm clocks by FreeTerra are ten and fifteen times more expensive, but allow you to set multiple alarms rather than just one.

Several others offer similar price points to Sleep Cycle, but all of the apps in this category seem to share Sleep Cycle’s main weakness: the interface. While the other apps mainly struggle with the uncanny valley—some use unnecessary custom UIs, while others use standard UI features in bizarre ways—Sleep Cycle at least has an agressively non-standard but self-consistent UI.

For me, the benefits of Sleep Cycle have been two-fold: first, I’ve been slowly increasing the amount of sleep I get to avoid feeling guilty when Sleep Cycle refuses to accept the 2-hour-and-fifty-minute supernap that’s sometimes all that stands between me and tomorrow. Second, even on days when I get five hours of sleep or less, Sleep Cycle can sometimes wake me at the right time to avoid the terminal grogginess that can otherwise result.


The Sleep Cycle alarm clock is a bio-alarm clock that analyzes your sleep patterns and wakes you when you are in the lightest sleep phase.

  • Hoot

    How does it differentiate between the motion of two sleeping people?

    • Ed

      In my experience, if you have the iPhone on your side of the bed, your body pretty much blocks out the movement of your partner’s, and it works pretty well.

      What is less useful is that for times when I’ve been sleeping alone, it only really registers my side of the bed, so if I end up moving to what is normally my partner’s side, I find it doesn’t pick up my movements, and so the natural wake up thing isn’t as useful.

      Next time that situation comes up I’m going to try putting it in the middle between the two sets of pillows and see if that improves things.

  • Andrea

    I think you missed the iTunes link!
    Pretty nice review! I’m going to try this app tonight :)

  • Arnoud

    I love this app but I’m not using it anymore because it has one big downside for me: it uses the vibrating alarm as well for waking you up and you cannot turn this off (choosing to only be woken up by sound). With vibration I don’t wake up comfortably at all anymore, very stressful. I still hope they will update the app someday and allow us to optionally turn vibration off.

  • Julia Altermann

    Very interesting app and I’d love to try it, but I think the fact that my cat walks and sleeps all over the bed all night might render it useless for me. :)

  • JP

    Sleep Cycle has one major weakness – it doesn’t support profiles. As someone who stays in two different places every week, this app is not nearly as useful as it could be. I can only use it at one or the other apartment as the beds are very different and the readings from the phone would be very different. Reason is the app must be “tuned” to the bed you’re sleeping in.

  • Adam

    I have been useless with alarms all my life, I sleep to heavily & I highly doubted this app when I purchased it, but I gave it a shot.

    How wrong was I? This App gets me out of be, usually 30 minutes earlier than I need to be, every morning WITHOUT FAIL, and because it wakes me during my lightest phase of sleep, I feel as fresh as a daisy!

    A must have App!

  • Pavlicko

    Glad you did a post on this Jonas –

    Let me just say – this app is UNBELIEVABLY AMAZING. I’ve been using it for a little over a month and it works perfect. Now it won’t wake you up PRECISELY on time, but it does an amazing job of picking that ‘almost awake’ state – it could be 10 minutes early or 40 min early – depending on your patterns.

    @Julia – as long as the cat doesn’t jump up and down right next to the iphone, you should be fine – I’d definitely give it a try.

    @Arnoud – can’t you just turn off vibration in general settings > sounds for alarm?

    I think part of why I love it so much are the Alarm songs themselves – they’re so soothing and fade up in volume – like the sunrise. I really do love this app.

  • Arnoud

    Good idea Pavlicko, though I don’t really feel like going into settings each time I want to use this alarm, plus after using it to set it back. A competitor of this app does have the option to turn off vibration.

  • Damien

    I have used this in the past and yes it’s awesome but is charging your iPhone every night hazardous to your battery? That’s my only fear!

  • Pingback: Best of AppStorm in March | Mac.AppStorm()

  • Pingback: Best of AppStorm in March | iPhone.AppStorm()

  • Pingback: Best of AppStorm in March | iPhoneApp Dev Blog()

  • Pingback: Best of AppStorm in March | Web.AppStorm()

  • Pingback: Another Night on the Road Equals Another Night of Useless Web Surfing……..()

  • Angie

    I have to get up at 4:00am and then again around 7:00am. Will this app work for me? I know I can’t set two alarms, but if I set it for the 7:00am wake up time and use another alarm for the 4:00 will it still work with me getting up and actually leaving the bed for an hour or so?

  • Mark Simpson

    I have just started to use this app, and I must say I’m impressed.

    Nice article with informative screenshots.