AS A PARENT, YOU

trust your child, right? You're sure that, when not under your watchful eye, your child would never do anything that could possibly be dangerous, like drive too fast or trade instant messages with some creepy Internet pervert, right? Um, right?

If you aren't so sure, new technology allows parents to keep a closer eye on their kids, whether it's in the car, online or on foot. This monitoring technology can offer some protection in situations as varied as cyber-bullying (computer software saves every instant message) to a flat tire (car recorders monitor location, and how long the vehicle has been in one place).

Whether you see this as a gross invasion of privacy (as your child surely will) or simply another tool to keep your kids safe is your call. But if you decide that your kids could benefit from your watchful eye even when you aren't around this technology can help make it happen:

Cellphone GPS Tracking

Want to make sure your child is really where he says he is? Programs from some cellphone providers enable you to locate both your child and his phone using the phone's GPS chip, says Kent German, a senior editor with electronics review site

. "They're accurate within a quarter of a mile," he says. The idea is that so long as your teen's phone is on and within your provider's coverage area, you can track his movements.

But there's a catch: Like other GPS devices, phone locators only work well when there's a clear view of the sky. Expect limited usability or skewed results if your teen is indoors or in a mountainous or urban area. "I was testing one in our [San Francisco] office, and it once placed me in the middle of the bay," German says.

Only a few providers are offering locator services so far, says German, but expect more to follow suit. Here's a rundown of what's available.

Monitoring the Computer

Computer monitoring software can be the most intrusive way to monitor your kids but also the best protection, says Parry Aftab, a New York-based Internet privacy lawyer and head of

, a group that educates children on the safe use of technology. Software keeps track of everything your child (or any other computer user) does, saving web histories, emails, chat-room conversations and instant messages. "A lot of parents use it just in case of problems like identity theft, cyber-bullying, or hacking," she says. "That in itself is a valuable use of the technology." Set it up to monitor 24-7 (which would capture the habits of everyone who uses the computer), or schedule it to run during times when you know your teen is likely to be using the computer unsupervised say, after school. The software stays hidden, so your child won't know she's being monitored.

But can your computer-savvy kid work around the software? Unless she has two computers and "hacker-grade" know-how, says Aftab, the answer is no. Do be on the alert for a reformatted hard drive, she cautions. That means your teen is trying unsuccessfully to remove the monitoring program. Of the programs available, she says, these two are the most effective:

Behind the Wheel

Sure, your teen is Mr. Cautious when driving with you in the car, but does he turn into Jeff Gordon when you're not around? Car-monitoring devices pull data from vehicle diagnostics everything from speed and distance to acceleration and accidents, says Kevin Massey, an associate editor with CNET. "It's empirical, so there's not a lot of room for error," he says. "So if your kid says he's been two miles away for a study session, and the car says he's been 40 miles away, well, you can confront him with that evidence."

There are two types of car-monitoring devices. Passive "black box" devices collect information for you to access at a later time, while real-time units work in conjunction with GPS to relay information to you as it occurs. Expect to pay more for the latter, says Massey, because they require a satellite connection. Both kinds are simple to install yourself they literally plug right into your car. Here's a sampling of what's available: