NEW YORK, Aug 29 (Reuters) - Morning grogginess may be a thing of the past thanks to bio-alarm clocks designed to wake sleepers at the perfect time.

An undated image courtesy of The Sleep Council. Morning grogginess may be a thing of the past thanks to bio-alarm clocks designed to wake sleepers at the perfect time. REUTERS/The Sleep Council/Handout

The clocks detect brainwaves or body movements and are programmed to wake sleepers during light sleep, which occurs periodically through the night.

“It felt like you’d already been awake for some time, and the clock just let you know it,” said Boris Abramov, 30, of Long Beach, California who used the Sleeptracker, which is worn on the wrist.

He had mixed reactions about the device. It worked well if he had a good night’s sleep but if he was stressed and worked late hours he would sleep through the alarm.

Sleep cycles vary from 90 to 110 minutes, so the bio-alarm clocks have a roughly 30-minute margin of error.

Other bio-alarms include SleepSmart, a headband with circuits that detect brainwaves during sleep, and the aXbo Sleep Phase Alarm Clock, which is a wristband that reads body movements.

Bio-alarms aren’t the only innovative wake-up devices to hit bedrooms. The Clocky has wheels that drive it around, forcing the sleeper to get out of bed and chase it. The Biobright alarm clock simulates a sunrise using a 60-watt light bulb.

And the Wake n’ Bacon wakes a person to the smell of breakfast. Frozen bacon is placed in the built-in oven the night before and starts sizzling 10 minutes before wake-up time.

But bio-alarm clocks are the only devices designed to detect sleep patterns. The Sleeptracker, introduced in March 2005, has an accelerometer that reads specific movements common during light sleep.

It was created by Lee Loree, an Atlanta-based financial analyst, after he observed his wife’s movements as she slept.

The similar aXbo clock “allows everyone to wake up like they wake up Saturday,” said Axel Ferro, an owner of the Austria-based firm that started selling clocks in January 2006.

Its alarm is a separate unit from the wristband and can be controlled wirelessly from bed. The clock can also be programmed for more than one sleeper and has different wake-up sounds.

The SleepSmart has sensors that read electrical brain waves that vary in frequency during light and heavy sleep. Four Brown University students designed it after one of them performed badly on an exam due to grogginess.

They formed a company called Axon Labs in Providence, Rhode Island in December 2004 and expect the device to become available “in the not too distant future,” according to Jason Donahue, its director of business development.

But despite the growing popularity of bio-alarm clocks at least one scientist is skeptical.

Dr. Gregory Belenky, a sleep expert at Washington State University Spokane, said light stage sleep isn’t the best time to be woken by an alarm.

“After a night’s sleep you are most likely to wake up out of a dream,” he said. “Dreams are most likely to have a spontaneous awakening, while (a light sleep stage) is the hardest time to wake a person up unnaturally.”

And without scientific testing, it’s impossible to know whether these devices are proven to work, he said.

“Maybe they’re the greatest thing since sliced bread. You just don’t know.”