Imagine a little $20 gadget that, just by wearing it, made you move.

A pedometer is just that – a device that rides with you, counting your steps throughout the day, nudging you ever so slyly.

“It’s like having this little tiny coach sitting on your shoulder, only it’s on your belt,” says Maggie Spilner, walking editor at Prevention magazine for 17 years and now a freelance writer and creator of walking tours (www.walkforallseasons.com).

“It’s a reminder that, ‘OK, I need to get up and walk somewhere – whatever it takes to move my pedometer up to a certain number,”‘ she says.

Pursuit of that certain number is something that physical therapist Jeff Wilkens has witnessed firsthand.

“It’s kind of like a little game people play with themselves,” says Wilkens, of the Sports Medicine Center at Froedtert & the Medical College of Wisconsin.

“Everybody’s got that competitive side to them. You get a little motivated to sneak in a few more steps. Pretty soon you’ve created a little bit of a lifestyle change,” he says.

Wilkens recalls a patient who wore a pedometer and had a goal of walking 10,000 steps – a number cited by researchers as a goal that brings health benefits.

“She would play games with herself,” Wilkens says. “She would park further away from the building. She would try to get up as often as she could during the workday. Little things that would get her up and moving. She would end up walking four to five miles a day by doing those little things.”

A 2005 study published in the journal Medicine & Science in Sports & Exercise found that wearing a pedometer meant taking an extra 2,000 steps in a day – which could mean the difference between gaining weight and maintaining or losing weight.

People should aim for 10,000 steps, but putting on the pedometer is a great way to see where you stand, Spilner says. Most people with desk jobs tend to log in 2,000 to 3,000 steps daily, she says.

Once you know how much you walk in a day, try to increase it, says Wendy Bumgardner, an avid walker and certified marathon walking coach who writes the walking guide for About.com.

Spilner recommends small changes, such as adding 500 steps to your daily goal.

“Once you’ve reached that goal, you put the marker up again,” she says.

Bumgardner suggests adding 2,000 steps a day.

“That’s about a mile per day. That’s something that most people can add into their day,” Bumgardner says. “Especially if they do it in little increments, like parking farther away from the door. There’s a lot of little ways. It really adds up.”

The simplest pedometers count steps, though most need to be programmed based on your stride to translate steps into miles. But in this era of ever-evolving gadgetry, you can get pedometers that count calories, keep tabs on blood pressure and heart rate, play music and even speak to you, announcing calories burned, time and distance.

So how do you choose the right pedometer? What do you need to look for?

Some key points to keep in mind:

¢ Watch the buttons. Some pedometers have the annoying design feature of a reset button that can be easily bumped – wiping out the record of the steps you’ve recorded for the day or week. To avoid this annoyance, Wilkens says to look for a pedometer with a “clamshell” cover over the reset button. For those whose goal is weight loss, he recommends a calorie-counting function.

¢ Wear it right. To work right, nearly every pedometer – there are a few exceptions – should hang straight up and down, Bumgardner says.

¢ Spilner also offers advice on wearing the device: “You have to position it on the waistband and in line with the hipbone, so every time you take a stride it feels the impact of your foot hitting the ground.”

¢ Stay with the basics. Spilner thinks that all you really need to do is count steps. “You don’t need to track your mileage. Two thousand steps equals a mile. If you walked 8,000 steps, you know you walked about four miles. You don’t need a machine to do that,” she says.

“A lot of people stumble over figuring out their stride length,” Spilner says. If you stick with a basic step-counting model, she says, there is no need to program for stride length. Just clip it on and start walking. But she adds that some people love gadgets that do a lot of things.

“If that’s what rings your bell, then sure, buy a high-tech one,” she says. But “if it confuses you, you’d be less likely to use it.”

¢ Is this thing working? With a good pedometer, age should not affect accuracy unless the battery is wearing out, Spilner says. “Accuracy stems from the mechanism inside. If you’re paying $15 or $20, it should be fairly accurate.”

Bumgardner recommends choosing one with what’s known as an accelerometer mechanism, though she points out that pedometers sometimes don’t list the type of mechanism. Especially if you’re buying online, you might have to hunt for this bit of information, she says.

¢ Strings attached. Make sure your pedometer has a string or strap, especially if you wear it all day. Who knows where it could land if it falls off, say, during a visit to the bathroom, Bumgardner says.

¢ It pays to pay. Expect to pay around $20 for a good pedometer. You’ll pay more for devices that talk, play music, count calories and keep records for you.

¢ Freebies and pedometers under $20, Bumgardner says, “tend not to be very accurate, and they don’t have a big life span for accuracy. After a year, it starts overcounting or undercounting steps.”

Says Spilner: “Freebies tend to not be as accurate – but if it gets you started, they’re great.”