FORT LAUDERDALE, Fla. -- As a private investigator, Jim Bender has tracked straying spouses and strung-out trust-fund babies, sometimes following them for days at a time.

But thanks to an innovative GPS device the size of a matchbox, he now can stake out a cheating husband without leaving his office. Or, as he has done the past few weeks, help a major company figure out who is draining the diesel fuel from its big rigs.

Technological advances have revolutionized the surveillance business, making devices smaller, cheaper and more effective than ever.

And they are not just for professional snoops such as Bender.

"Anybody can be a spy now," said Todd Myers, president of Computer Sights, a computer-support and surveillance-supply store in Fort Lauderdale. All it takes is a few hundred dollars, an Internet connection and a little curiosity.

Think that device on the wall is just a smoke detector? Look closer and you'll see a camera's lens. Those floodlights hanging from the ceiling? They're more illuminating than you think.

For private investigators such as Bender, the improved equipment has led to improved service.

However, it also has given Peeping Toms a new way to gawk.

Spencer Krumholz, marketing director of World Imports International in Pompano Beach, Fla., faces a lawsuit from two of the company's employees.

He is accused of placing a hidden camera in the ceiling of the women's bathroom, according to court records.

Last year, a Connecticut man wired a shampoo bottle with a tiny camera so he could watch his two female roommates as they showered, according to police. Someone discovered the camera, and Steven Thibodeau was arrested on voyeurism charges.

He later admitted to the crime and received probation. A judge ordered him to stay away from cameras and computers.

For the most part, however, the equipment is used by people to protect their interests.

A few months back, a well-tailored businessman who suspected his wife of cheating on him bought from Myers a $300 WiLife digital clock equipped with a spy camera. The man put the clock on his bedside nightstand, and the images it captured were sent, through the power lines, to a computer.

The executive set up the system to alert him, via text message, if there was movement in the master bedroom while he was at work.

The next day, his cell phone went off. With just a few clicks of his office computer, he pulled up the video.

There was his wife and another man "making whoopie" on the couple's bed, Myers said.

The husband copied the feed and sent it off to his attorney, who drew up the divorce papers. The video saved the man millions in alimony, he later told Myers.

"I'd much rather have given it to him for free and taken a percentage of his savings," Myers said.

Bender, who works out of Fort Lauderdale, spent the last few weeks in central Florida on assignment for a prominent distribution company based there.

The owner called him in because of a recurring problem with a 70-gallon diesel tractor-trailer. It would leave the facility at night with a full tank and return just three-quarters full, despite only a handful of miles difference on the odometer.

At $4.20 or so a gallon, diesel is a valuable commodity, and the owner didn't like getting ripped off.

So he brought in Bender to sort out who was stealing from the company, and who was buying the stolen fuel.

In the past, such stakeouts could take hundreds of hours. Now, it's as easy as hiding the GPS device in the truck's wheel well and waiting for it to return.

"The tracking devices that they had a year ago, those things were the size of a loaf of bread," Bender said.

He has also used the device to track the daughter of a prominent family to crack houses.

"This was a huge step forward in making it affordable and more covert. I've gotten three or four new clients based on this technology in the last few weeks," he said.

Sharron Lambert just wanted to know the truth about her husband.

The Birmingham, Ala., woman suspected that he was cheating on her a few years ago so she dropped a GPS device in his car.

One day, when her husband thought she was at work, she tracked her husband down, finding him in the arms of his mistress.

"By the time I caught him, I already suspected the worst," Lambert said. "All the emotional stuff was already there. Now, I could do whatever I need to do about it."

It was a liberating experience. So much so that Lambert started a surveillance-supply business and became known as the "Gadget Lady." She sells GPS devices, audio and video recorders, caller-ID scramblers and computer-keystroke monitoring software.

"I sell things you would use to obtain the truth," Lambert said.

While surveillance technology has exploded, the laws controlling it have changed little.

Myers has at least once kicked out people who asked him to help them break the law regarding making covert recordings.

Certain acts, such as voyeurism, are illegal regardless of the technology.

In late 2006, police in Davie, Fla., arrested a man who they say used a camera hidden in a hat to peek up women's skirts in Kmart.

Jon Fletcher was charged with voyeurism, a misdemeanor. He awaits trial.