THE GIZMO:

Nintendo Wii Fit.

LAZY BONES ARISE! Nintendo has a great new way to get you up off your duff and moving your stuff. Wii Fit goes on sale everywhere today, and it's going to be huge - though you won't be, after using it diligently for a while.

MAKING A GAME OF IT: Working with the super-popular Nintendo Wii game system (which sells for $249) and a TV set of your choice, Wii Fit treats exercise as an entertainment challenge. It pumps you up with cute game settings and characters (including your customized, on-screen "Mii" persona) and perky music. And it scores points and serves up rewards to those who do well (or even just persevere) with its yoga, aerobics, strength training and balance regimens.

The $89.99 package includes a software disc that's installed in the Wii system and the two-years-in-perfecting Wii Balance Board, a 12-by-20-inch, 8 1/2-pound platform (with a 330-pound weight limit) that is at once home base of your new mini-gym and the game controller.

The board works its magic by sensing your weight and your shifts in movement and balance as you mimic the Warrior or Tree position demonstrated by your cartoony yoga coach, or bob and weave your on-screen Mii in a downhill ski slalom course.

SETTING THE GROUND RULES: Take your shoes off for starters - and your socks too, perhaps.

You'll be doing lots of standing, leaning and stepping on and off the Balance Board (the stepping routines are almost as much fun as "Dance Dance Revolution"). But this device is not meant to be jumped up and down on, even when trying to put some body English into the ski jump competition (just crouch, then bounce up - VERY evenly).

There are foot extenders for use on a thick rug. And don't forget to clear a 3-foot (or more) circle around the board, so you don't bang into things. How

you'll keep a curious cat from interfering with your moves is another matter.

Like the Wii remote, which you'll also be using, the battery-operated board makes a wireless connection to the Wii game system. Only one board at a time works with the game system, and it will need to be resynchronized if used on another Wii system or with a Fit-compatible game such as Namco Bandi Games' "We Ski."

MY FIRST TRAINER: First time using the Wii Fit, it asks for your age and height, then measures your weight to calculate your Body Mass Index or BMI. The program then rates you as underweight, overweight or just right, and asks you to set a goal of weight loss or gain. It charts your progress every time you use it but keeps the stats password-protected.

The software also uses all this information to develop an age- and weight-appropriate set of challenges. When you go jogging through Wii Fit Island - running in place off the board using the Wii remote as a pedometer - the on-screen trainer your Mii trails won't move unduly fast, at least not at first.

But be forewarned, while Fit is based on health science and is the first game system endorsed by the President's Council on Physical Fitness and Sports, it doesn't have all the answers a real fitness coach or physician might provide.

That BMI rating system is only appropriate for ages 20 and above. The system also rates younger users but can't tell that a bulked-up 10-year-old is about to have a growth spurt.

Nintendo recently earned some bad publicity in Britain, where Wii Fit has been available since April. A father went ballistic, complaining the system had inaccurately rated his sporty, pre-adolescent daughter as fat, causing her psychological trauma. (Yo, dad, read the fine print in the owner's manual.)

And I, frankly, got just a little upset after the system asked me to perform a preliminary balance test that wasn't clearly explained. After I failed miserably, it told me my Wii Fit Age was 15 years older than my chronological age and warned: "Your body is much weaker than you should be." I had a lot of proving to do.

THE FUN AND GAMES: After picking the look of your on-screen Avatar and that of your coach (male or female), it's off to the gym, or the sports field, or wherever.

The nice thing about this package is that (like the Wii Game System) it's "all ages/all lifestyles" appropriate and is likely to see use everywhere from nursery schools to retirement communities.

My super-active wife, Abbe, had a good time with muscle toning, strength-training exercises and mimicking the yoga moves of her on-screen coach. Abbe pointed out that the positions were pretty accurately portrayed, though Fit doesn't delve into the holistic or meditative qualities of yoga, of course.

The far less committed exerciser in the family (me Mii) got my heart pumping with persuasively fun (it hardly seemed like work) aerobic activities like Basic Step, Rhythm Boxing and Hula Hoop (work those hips!).

I also had a good time with body-limbering, balance-game pursuits such as Table Tilt, Tightrope Walk and Soccer Heading (which had a reminder that this is a video game: Unwelcome objects like soccer shoes and balled-up pandas are tossed your way if you don't connect with the balls).

Just like a private trainer, Fit serves up lots of encouragement, keeps track of total exercise minutes and periodically cues you to take a break and drink some water. No, it won't gab with you about current TV shows and movies, or how lousy its love life has been lately.

Sometimes less information is a good thing.

SCORING A WII: Nintendo claims there will be ample supply of Wii Fit units to sell to the current base of about 9.5 million U.S. Wii console owners. But if you don't already own a Wii, you'll have to be on your toes to score a system - still in short supply and never, ever discounted. Availability should improve after July, when Nintendo will ramp up production. *

E-mail Jonathan Takiff at takiffj@ phillynews.com.