Photo: by Jens Mortensen

The dime-sized tracking devices that movie spies stick on villains’ cars don’t exist (that we know of). But there are some fairly small options for keeping tabs on your closest enemies.

1. Lightning GPS Spark Nano

Not much bigger than a Zippo, the Spark determines its position via cell towers. Just tuck it into something you need to track and follow along on the intuitive web client that updates in real time or at set intervals. Even with 30-second updates and stashed in a backpack inside a car, the Spark was fast and sensitive enough to show us the moment our significant other (a willing participant) missed a turn on her way home.

WIRED Push notifications warn if the Spark crosses one of the Geo Fences (no-go zones) you’ve designated.

TIRED Must export data for replay. Kinda creepy.

$150, plus $70 activation fee and contract (starting at $210 for three months), lightninggps.com

Rating: 9 out of 10

2. iTrail GPS Passive Logger

This unit ditches the onboard transmitter and instead records location data for download once you retrieve the device. While that means no real-time monitoring, the upside is a tiny form factor about the size of a tea bag—truly concealable. The Logger returned the finest location accuracy of the bunch, and the Google Earth-based software was the easiest and most entertaining to use.

WIRED No service plan required. Automatic pop-up info during replay details how much time was spent at each stop along the journey.

TIRED After-the-fact info means no catching people in the act or recovering your stolen luggage. Retrieval is just another chance to get caught. No Mac compatibility.

$190, myitrail.com

Rating: 8 out of 10

3. Livewire FastTrac

Another cell-based solution, the FastTrac is nearly twice the size of the Spark but adds a motion sensor and double the standby time (10 days). Web-based software offers replay and address lookup, so you’ll know if 450 Elm Street is a shoe store, a café, or something else altogether. Need to communicate with someone you’re tracking? Skype integration makes it easy. No-button operation is idiot-proof, but this is a lot of power to put in the hands of an idiot.

WIRED No contract required. SMS alerts when unit exceeds a set speed, so you’ll know if the parking guys have taken your dad’s Ferrari out for a spin.

TIRED Expensive. Very creepy.

$400, plus $25 activation fee and $39.95/month, brickhousesecurity.com

Rating: 7 out of 10

Buggin’ Out

Photo: by Jens Mortensen

Think somebody’s watching you? The Brickhouse Security Cell Phone & Gps Detector ($295) will tell you if you’re crazy—or drive you there itself. The walkie-talkie-sized widget detects signals from GPS trackers and listening devices. This would be helpful, or at least entertaining, if cell phones didn’t often emit the same signals. Is it alerting you to a bug in your apartment or just your neighbor’s HTC Incredible? But if you can eliminate the known devices, it will indeed spot uninvited broadcasting. A quick scan of the cabin could add muscle to airline requests to shut off cell phones. But it’s of little use to people whose biggest privacy concerns are their Facebook settings (most of us).—J.H.