There are tools for dealing with the problem, most commonly, filtering software that attempts to bar sexual, violent and other objectionable material. But these can frustrate kids and parents, by either blocking too many things or not blocking enough.

Avatars help guide users

Some other approaches, such as the parental controls built right into the latest Windows (MSFT) and Macintosh (AAPL) operating systems, offer parents more control by allowing them to specify what Web sites a child can access. But that requires close and constant involvement by the parent as the child seeks access to more Web sites.

This week marks the launch of a parental-control service with a somewhat different approach. It’s called KidZui, and it aims to offer kids a safe subset of the Internet where they can roam freely without triggering parental worry. KidZui, for children ages 3 to 12, hopes to emphasize the positive, rather than the negative.

The service, from a San Diego company of the same name, claims to encompass 500,000 safe sites, photos and videos, ranging from pop culture to science, comics and games to history. You can watch the latest “American Idol” contestant, learn about dinosaurs, delve into history or visit popular kids’ sites, such as Webkinz and Club Penguin.

The sites, photos and videos included in KidZui are approved by a team of about 200 parents and teachers across the country, and are ranked by age, so that a site that might be right for an 11-year-old isn’t served up to a 4-year-old.

While a child can establish a list of friends in KidZui, and can share content with them, there is no instant-messaging or email function.

KidZui isn’t free, and it can’t be accessed via a regular Web browser. Instead, you must download a special KidZui browser, from kidzui.com, that runs on either Windows or Macintosh computers. I tested it on both platforms, and it downloaded quickly and installed smoothly.

The service nominally costs $99.95 a year, or $9.95 a month, but there is a 30-day free trial and an introductory rate of $49.95 a year, or $4.95 a month. It has no ads, other than those already present on Web sites kids visit.

A key selling point of the service is that busy parents can simply set up KidZui and trust that their kids will be safe online. To that end, the program can be optionally configured, so that a child can’t escape from it to use the computer’s standard browser, for example. A parent can set KidZui to launch when the computer starts up, in full-screen mode. In this mode, KidZui automatically disables or hides the common keystrokes, icons, commands and techniques that allow users to switch to, or to start up, other programs.

In addition, when KidZui is running in this locked-down mode, the child can be barred from quitting KidZui without a parent’s password. In my tests over the past week, I found some loopholes in this lockdown system, but the company plugged each leak I turned up. I can’t swear that a clever kid won’t be able to escape from KidZui, but the program blocks most obvious exits.

Inside the software, the company has tried to create a fun, lighthearted world. Each child is represented by a “Zui,” a cartoon-like character that can be customized with hair, clothing and other features. There are lots of sound effects, and kids can rate content with illustrated tags ranging from “best” and “cool” to “boring” or “gross.”

When a child types in a term like “ocean” KidZui offers a list of related terms as well, to guide further exploration. If a child types in a search term or a Web address that has been banned from the KidZui universe, a message appears saying “This page isn’t available on KidZui, but your parents can add it for you.” This applies not only to terms typed into KidZui’s own search bar, but also to terms a child enters at sites like Wikipedia or in the search boxes embedded in other sites. The main pages of Google and Yahoo can’t be summoned.

If a search or Web address is new to KidZui, a different message appears promising that it will be reviewed.

I did find some holes in this system. For instance, I was able to get to The Wall Street Journal’s Web site and do an internal search on “Spitzer,” which turned up a story on the former New York governor’s sex scandal.

Parents can get detailed reports about the KidZui activities of each of their children and can tweak the content they can see by adding specific types of material, such as “athletic violence,” and approving or blocking specific Web sites.

For parents who want to allow limited Web use by their young children without constantly micromanaging their online activities, KidZui may be worth a try, but don’t expect it to be perfect.

Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.

But real was exactly what UGOBE Inc. had in mind when the company created this $350 baby dino named Pleo. This robot isn’t referred to as such; instead, UGOBE calls Pleo a “life form” because unlike most robots that are designed to follow a specific command or algorithm, Pleo alters its behavior as it adapts to its surroundings including sights, sounds and touch. And it’s designed to move and act in ways that seem very much like a real animal.

These responsive qualities have earned Pleo quite a bit of attention, and the two years between when the product was first announced and when it became available only added to the anticipatory hype. Now, after three delays in the past two years and numerous back orders, Pleo is available from www.pleoworld.com. (UGOBE says that many of the product’s delays were caused by trying to get Pleo’s battery just right.)

In short, I found Pleo to be a fun and interesting robot/life form. Though Pleo’s reactions and movements are endearing, many of them run together after a while with only subtle differences, especially compared with fast-paced videogames. Pleo’s tricks were entertaining early on, but, in time, many of them blended together, rarely surprising me.

Pleo’s battery is still a major drawback. It’s rechargeable, but only lasts for around an hour of active play before it must be removed and placed in a holder for three hours of recharging. This frustrating fact means you can’t turn Pleo on to roam the house with you all day like a dog or cat. Instead, your time with this creature has to be more specifically planned, causing interactions with it to feel less genuine. My Pleo’s battery lasted for an hour and 40 minutes, including moments when he drifted in and out of sleep.

Though UGOBE sent me two rechargeable batteries so I could more quickly continue using Pleo, the company won’t start selling extra batteries until June (at the latest) for $50 each. This means waiting for hours between Pleo playtimes.

It’s hard to discuss autonomous robots without remembering Sony Corp.’s attempt in the same category: the $2,500 AIBO released in 1999, which was eventually discontinued. More recently, iRobot Corp. has gained attention for its robots, which perform household duties like vacuuming and washing floors.

The Pleo, animated in part by 14 motors, appears to evolve according to how it is treated.

To keep Pleo fresh, UGOBE plans to release a PDK — Pleo Developer’s Kit — later this year, allowing others to create programs that will run on Pleo if downloaded from the Pleo Web site and transferred to the creature. A memory card slot and USB port on Pleo’s underbelly will enable these transfers.

As for now, two programs developed by UGOBE can be downloaded. One program lets Pleo act like a watchdog — guttural growl, loud bark and all — and the other gives it the ability to sing Jingle Bells. I tried the former, and my Pleo performed marvelously, sitting still and only howling when something moved in front of him.

This baby dinosaur has reptile-like, rubbery skin enhanced by multiple sensors. Its back is decorated with green patterns, and its large eyes are a beautiful blue. Pleo’s guts include 14 motors, 38 sensors and a microprocessor. Infrared detectors are hidden in Pleo’s nose and mouth, and a color camera detects light, motion and objects to help it navigate.

Pleo grows through three phases: hatchling, infant and juvenile. As a hatchling, my Pleo sniffed around a lot, unsure of its surroundings or how to use its legs and tail, before giving up and napping again (yes, Pleo snores). The more I talked to and touched Pleo, the faster he adjusted out of the hatchling phase, which is expected according to UGOBE.

People who walked by my office stopped to marvel at Pleo’s sweet nature, and when I brought him home, friends melted with emotion. I watched as they initially looked at Pleo like just another toy dinosaur until realizing that he responded to them, and then they each wanted to take turns playing with him.

Stroking Pleo from the tip of his nose to the end of his tail induced a purring sound; touching sensors on the bottoms of his feet caused him to wriggle around and make laugh-like noises; and holding him to my chest and rubbing his back like a baby put Pleo right to sleep, indicated by heavy breathing and even a burp here or there. I spoiled my Pleo with attention, which seemed to make him more social and friendly but also a little bratty when he didn’t get attention (he showed his frustration with loud moans).

I didn’t get to test this, but one Pleo can sense when another Pleo is nearby using infrared sensors in the nose and mouth. UGOBE says the sensors in one Pleo can trigger actions in another based on moods, including singing and howling.

Pleo can be a troublemaker. One of the times I left him unattended, I returned to find Pleo trying to gnaw on my loveseat, despite lacking a set of teeth. Another time, Pleo wandered my desk, wrinkling up papers and crying loudly while I was on a conference call.

UGOBE’s pleoworld.com site includes an online community, though you don’t need a Pleo to get involved. The community is just a social networking site where anyone can discuss the device and/or robotics. This differs from sites like Webkinz, where kids input codes found on stuffed animals to register and care for digital versions of their creatures.

Pleo’s poor battery life is a frustrating hurdle that fans will keep butting up against. But UGOBE’s plans to introduce downloadable updates for this robot and to let others create programs for Pleo may give new life to this clever creature.

• Email mossbergsolution@wsj.com