The Sleeptracker Pro is a bulky wristwatch designed to detect its wearer's sleep cycles, so it can help determine the optimal time and conditions for a great night's rest. Nice. Now I know I don't sleep so well when I get nudged all night by a bulky wristwatch.

Usually when I come across a gadget I wouldn't recommend - a voice-activated grocery list generator here, a purported eyesight-enhancement kit there - I don't bother writing about it.

But while I wouldn't actually encourage anyone to spend $179 on the Sleeptracker Pro, its underlying idea is worth watching. Because it indicates that we can hack our sleep, as if mysterious slumber is another system whose controls can be tweaked.

The watch - which rises 3/4 of an inch off the wrist - is gigantic largely because it has an accelerometer inside to detect when it's moving. The principle is that this happens when the wearer is in the lightest phase in the sleep cycle, nearly awake.

So if you need to start your day by 7 a.m., you set the watch's alarm for that time - but you also select whether you'd be willing to wake up anywhere from 10 to 90 minutes earlier if the watch detects a better moment.

The thinking is that it's better to have the watch vibrate or chirp at 6:48 if it senses you're in a near-waking light sleep - from which you could spring out of bed belting show tunes - than to drone on until 7 and risk falling into a deeper sleep from which you'd stir groggily.

In theory, this sounds good. When it comes to sleep, sometimes less is more.

In practice, I didn't feel any more invigorated than usual, and I questioned whether the watch was making the right call. Who's to say I wouldn't have felt just as good or just as drowsy lying there for 12 more minutes?

And more importantly, every night I wore it would have been a lot more restful if I had just never strapped that paperweight to my wrist in the first place. In case I forgot to mention it: The Sleeptracker Pro is huge.

The Sleeptracker also was, of course, powerless over my real alarm clock: my 2-year-old daughter. One morning when I had the alarm set for 7 and she called out at 6:42, I had to laugh when, as I was sliding out of bed, the watch buzzed as if to say, Hey, seems like you're in a light-enough sleep to go ahead and start the day! Thanks, pal.

Sure, that's no fault of the device, but it's a reflection of how useful the thing really is. Parents should think carefully before spending $179 for a gadget that mocks, albeit inadvertently, their sleep deprivation.

If this still appeals to you, save $30 by opting for the $149 non-Pro version of the Sleeptracker, which came out two years before last fall's launch of the Pro. The regular Sleeptracker has an audible alarm only and doesn't vibrate, but that gives it a smaller battery and less bulk.

Another supposed advantage of the Pro is that it lets you clamp a USB attachment onto the watch so you can download a record of your sleep cycles during the night. The longer the interval between these moments, the better you slept, supposedly.

The Sleeptracker's PC software lets you annotate the data with factors that might have contributed to how deeply or poorly you dozed - like late-night alcohol, food or, um, exercise - so you can engineer optimal rests. But even without the software, the watch itself each morning displays how far apart your light-sleep phases occurred.

Even that is unnecessary. Bedrooms tend to have clocks, so the Sleeptracker should lose the watch display and its accompanying clunkiness. Instead the device should be housed in a much thinner strap with nothing but a snooze/alarm on-off button. The alarm could be quickly set on a PC and relayed to the Sleeptracker over wireless or USB.

Until then, save your money for coffee.

---

On the Net:

http://www.sleeptracker.com