» What is it: A GPS device about 3 inches long and an inch wide that you can track via computer or smartphone.

» How it works: Attach the device to a dog, a suitcase, a bike, a car, a marathoner, a child, a husband, a wife — whatever you want to track. When you want to see where the device is, you simply call up the my.garmin.com Web page or go to the Android or iPhone app and click to locate the device on a map. After purchase, you must register and activate your locator. Some online reviews said this was a touchy process; I had no problem. To maintain an account after one year costs about $50.

» The good: It can track a car in a suburban setting and follow its movements so closely that you can tell when it stops for a traffic light and whether it stays within the speed limit. By creating what Garmin calls a "geofence," you can receive email notification whenever the car enters or exits a given area. Despite its implications for familial espionage, it has great travel applications, such as when you let your teen take that school trip or when you want to track fellow travelers while on the road.

» The bad: When trying to track co-workers in a big-city setting, the GPS signal was unable to navigate the tall buildings, so the device reverted to positioning via cell-tower signals. This gave approximate locations rather than exact GPS positioning, so the device can be limited by terrain. Also, the more notifications you demand from the device, the quicker the battery runs out, but geofences help conserve power.

» Cost: $199.99

» Available from: garmin.com (and other online retailers; as always, shop around)

Chicago Tribune, www.chicagotribune.com