If you're like me, an alarm clock wakes you at the same time five days a week. Usually I feel like I've been kicked in the head by a mule. I have to sit on the bed for a spell before my brain realizes that the eyes are open and it's time to start processing data. But on other days, I awake fully refreshed. I go to bed at roughly the same time every night, however, and the morning's outcome doesn't correlate with the time at which my head actually hits the pillow.
I never gave the "mule kick" phenomenon much thought until I read about the Sleeptracker from Innovative Sleep Solutions, a device that claims to have powers and abilities far beyond those of mortal alarm clocks: instead of sounding klaxons at an arbitrary time, it wakes you at the optimal time for you, and you awake feeling fully refreshed. Sounds like hokum, you say? That's what I thought.
Deep Background on Dozing -- First, a bit about sleep cycles. As we sleep, the body passes through a set of cycles that govern sleep's restfulness, recuperative powers, and dreams. Sleep is considered to be divided into five stages of varying levels of activity and restfulness.
Stage 1 is a transitional state in which the body relaxes and the heart rate slows, until you arrive at stage 2, or baseline sleep. From stage 2 the sleep becomes increasingly relaxed and the heart rate slows further, until you reach stages 3 and 4, or delta sleep; delta sleep is the deepest sleep. It's very hard to wake a person in delta sleep, and such a person is usually disoriented to find themselves awake. Stage 5 is REM, or "rapid eye movement," the stage in which dreams occur. REM sleep is considerably less deep than stage 4; it's actually closer to awake than stage 2's baseline sleep. After the REM stage, we return to stage 1 and the cycle begins anew. The average adult goes through four to five such cycles over the course of eight hours' sleep.
Over the course of a night's sleep, the overall cycle lessens in duration and depth, until we finally awake in the morning. While the first cycle might take two hours, thirty minutes of which are in delta sleep, the last cycle might be only half an hour and be no deeper than Stage 2.
Counting Sleep from Your Wrist -- The Sleeptracker looks and is worn like a wristwatch, but not a particularly flashy or stylish one - by all appearances it's an average, non-interesting digital watch. It doesn't have features you'd normally expect in a digital watch - no stopwatch, 24-hour clock, countdown timer or multiple time zones - because it's really marketed as a sleep aid.
To use the Sleeptracker, you set the time at which you want to be awake - probably the time for which you'd set a normal alarm clock. You also set the interval leading up to the alarm time, during which the Sleeptracker may wake you, and the time at which you'll go to bed at night. (This last time is required so that it knows when to start monitoring.) During the night the Sleeptracker's accelerometer monitors your physical activity, and from that determines the peaks in your sleep cycles. As your target wake time approaches, the alarm goes off at a time during the specified interval in which you are closest to being awake. If your sleep cycle doesn't supply an "almost awake" peak during the interval, Sleeptracker goes off at the designated wake time. It also has a Data screen that lets you review the peaks in the last night's sleep cycles.
Does it work? Actually, it does. If I set the Sleeptracker to wake me up no later than 6:30 AM, with a wake interval of 30 minutes, it usually gets me up around 6:20, without that mule-kicked sensation. (I know from experience that, had my normal alarm gone off at 6:30, I'd sit on the bed for 15 to 20 minutes waiting for the cobwebs to clear.) To wake up 10 minutes earlier and feel fine, well, it feels wrong on some basic cosmic level. What's more, the next day I feel generally more alert, drink less coffee to "stay sharp," and I don't sneak a nap when going out to "get some air."
So, it works, but it's not a panacea for getting enough sleep, and it doesn't cure my penchant for being a night owl. It doesn't help you get to sleep at a decent hour, and it doesn't make four hours feel like eight. My wife wishes it had a buzz option instead of beeping. (She doesn't seem to mind our clock radio alarm, perhaps because she's used to ignoring it.) On a couple occasions I slept through the beeping, because my arm was either under several layers of blankets or a couple pillows; my wife wouldn't like a louder beep, but it might be a good idea for me.
As a $150 wristwatch, Sleeptracker seems ludicrously expensive. As a $150 sleep aid that helps you wake up feeling refreshed, it might be a fair price. Adjust your expectations accordingly. [Alternatively, Tonya and I highly recommend falling asleep to an audio book, which helps us fall asleep faster and wake up more easily. See "iPods Defeating Insomnia" in TidBITS-768. -Adam]
Sleeptracker does what it claims: it wakes you up at the optimal time. My inner geek is always excited by new opportunities for optimization, but I still wonder... what if I just went to bed at a decent hour?
[Andrew Laurence is a writer and editor at modmini.com, which provides in-depth Mac mini reviews and analysis.]