In 2008, American pet owners spent $43 billion on their animals. Walk into any pet store and it is easy to see how — $60 brushes, $200 designer cat scratchers, $450 midcentury dog beds. But the market for pet gadgets has been dismal, in large part because of the abundance of novelty goods that are more expensive than practical. I mean, who needs a gizmo that can translate your dog’s barks?

This doesn’t mean useful pet gadgets don’t exist. As a certified dog trainer, as well as a cat rescuer, I’ve seen and used my fair share of high-tech pet gear. Some of it has been useful, some of it laughable. Those that get it right though, alleviate a problem you may not have even known you had. And like your cell phone, once you use them, you won’t know how you lived without them.

Litter-Robot

One thing I constantly hear while rescuing cats is, “I love them, but I hate litter boxes.” Who doesn’t? Try smart engineering instead. Plenty of litter boxes have claimed automated self-cleaning, but the Litter-Robot is the only one I’ve seen that delivers. A weight sensor marks when your feline enters and leaves the device, which looks a little like the Death Star. The Litter-Robot then counts down from seven minutes and, as long as the sensor hasn’t been activated again, the globe begins to spin counterclockwise.

Gravity pushes the litter — any clumping or scoopable type — over a sifter, which separates the clean from the soiled. Waste is dispensed into a plastic bag in the bottom of the machine. Once the bag is full (about a week of single-cat use) you open the drawer, pull out the bag, tie it up and throw it out.

There are two drawbacks to the Litter-Robot: its price, $329 (litter-robot.com), and its size — 29-by-22-by-24 inches — but that is a small price and a minor loss of floor space for never having to clean a litter box again.

Zoombak

If you are lucky enough to live on a large plot of land, your dog could, and probably does, spend the entire day outside. So where does your pup venture? Zoombak is a $99 (zoombak.com) GPS-enabled device that attaches to your dog’s collar.

It lets you zero in on where sleeping dogs lie at any moment over the Web or your cell phone, or via a live customer care representative.

You can also sketch out safety zones on a Google-like map, and receive text messages if your hound throws caution to the wind and hightails it out of the immediate area. If your dog gets lost, you can pinpoint its coordinates online before going to retrieve it. Just don’t skip the $10 monthly service charge, or the device becomes useless. Zoombak works only where there is a T-Mobile signal.

Komfort Pets Carrier

Traveling with your pet is often unavoidable. And while you may be enjoying the air-conditioning in your automobile, it may not be making it to the plastic box your pet is sitting in at the back of the car. One of the easiest ways to ensure your traveling companion isn’t miserable is to set it up in a Komfort Pets Carrier, $149 (komfortpets.com).

The climate-controlled carrier features conductive plates in the floor that automatically turn on if the temperature in the carrier goes below 56 degrees. If the temperature gets too high (70 degrees and up), a fan gently blows cool air into the carrier, and the floor cools as well. Unfortunately, Komfort Pets hasn’t gotten airline approval to plug in within cargo holds, so it can’t be used while airborne.

SNIF Tag

Ever wonder if your dog walker is really giving your pup a workout? The SNIF Tag, $299 (sniftag.com), is the equivalent of the baby cam for neurotic dog owners. A small tag attached to your dog’s collar uses a three-axis accelerometer and motion sensor software to determine what your dog is doing — walking, running, sleeping — and records the information in the tag’s flash drive.

Back home, SNIF Tag’s base station connects to your home network via an Ethernet cable, and uploads all the information to a Web site. The site breaks down your dog’s activity by minute, hour, day, week and month, and lets you determine, by breed and age, whether your dog is getting enough exercise.

The tag also features a social component: When your canine companion has interacted with another SNIF tag wearer, you can contact the owner of your pet’s new friend to set up another play date. One problem: finding enough owners who are willing to spend $300 on the device.

QuickFinder Deluxe

If you’ve ever had to cut a pet’s nails, you know how stressful it can be, given the risk of cutting into the quick and nicking the blood vessels. The QuickFinder Deluxe, $24 (quickfinderclipper .com) uses a patented sensor that detects heat radiating from the blood vessels. A miniature traffic light on the clipper lets you know when it’s safe to cut. Red, quick up ahead. Yellow, proceed with caution. Green, clip away. You’re still in charge of keeping your cat from squirming.

Portable Extractor

If a cat urinates and no one sees it — it still reeks. For those hidden urine stains that can be found only with CSI-worthy gadgetry, there’s Dirt Devil’s Purpose for Pets Portable Extractor, $109 (dirtdevil.com). The carpet cleaner has blacklight LEDs on the scrub brush that illuminate hidden stains in carpets and furniture. I can only imagine how frightening it may be to discover your entire rug is glowing in the dark.

Petporte

On “America’s Funniest Home Videos,” there’s always the family that finds a dog or raccoon stuck in a cat door. Don’t be that family. The Petporte (petporte .com) uses the radio frequency from a microchip embedded in your cat (or small dog) to ensure other beasts stay out.

The clear plastic door remains locked until a sensor reads your pet’s microchip. Petporte works only with European microchips, but this fall the company will release a door that can read American 10-digit chips. Light sensors allow pet owners to program the door to lock at certain hours so your pet does not go out for a nightcap.