Name: Garmin GTU 10 GPS Locator
What it is: 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: I tracked my wife's car (with her permission) in a suburban setting and was able to follow her movements so closely that I could even tell when she had to stop for a traffic light on the way to work and whether she was breaking the speed limit. By creating what Garmin calls a geofence, I also received email notification whenever her car entered or exited a given area. The device worked so well that I was able to deduce when she went to Burger King for lunch. (She said she got a salad.) Despite its implications for familial espionage, I can see great travel applications for this, such as when you let your teen take that school trip and you know she won't call often enough 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.
Available from: garmin.com (and other online retailers; as always, shop around)