Sensors shake up gadgets

— -- Entrepreneur James Park's new gizmo can monitor sleep habits and daily exercise, automatically.

The $99 Fitbit Tracker, coming in January, is a small device that knows both how many calories you burned and how long it took you to fall asleep. How does Fitbit accomplish all of this? With a tiny motion sensor, called an accelerometer.

The little tech add-on, which costs manufacturers all of about $1, has become the latest go-go accessory in Gadget Land, popularized by Nintendo's Wii gaming console and Apple's iPhone. Accelerometers are basically chips for devices that measure acceleration and gravity forces. Tech firms can buy the chips from industrial supply vendors.

An accelerometer on Olympus' new $299 1050 Stylus SW lets you view pictures you've just taken by tapping the back of the camera. Similarly, you can shake Apple's new iPod Nano to advance to the next song. Or wear the Fitbit to learn that you stopped tossing and turning shortly after midnight.

"With an accelerometer, motion is much more precise," Fitbit CEO Park says. "A pedometer, for instance, uses mechanical mechanisms for counting steps. It can convert steps into calories, but it doesn't take movement into account."

Accelerometers have been around for a while, in airplanes and autos. They are also used in laptops, where they help prevent failure of the hard drive. They warn the drive, in effect, that the computer is about to be dropped and temporarily put it to sleep to save the data.

Charles Hitchcock, a New Hampshire-based product designer, has spent years making devices that connect to musical instruments for recording and mixing music. Cowbell Plus is his first with an accelerometer. Created for the iPhone and iPod Touch, it's a way to tap along to iTunes music with virtual cowbells, tambourines and hand claps.

"Suddenly, there's this whole new form of motion to capture and have fun with, a new way people can be expressive," says Hitchcock, co-founder of Frontier Design Group.

In Barcelona, Xavier Carrillo Costa, CEO of game designer Digital Legends, just put the finishing touches on his first iPhone game, Kroll, which went on sale Tuesday at iTunes for $7.99.