Shiva Nathan spends a lot of time thinking about a robotic arm. And when he does, the arm begins to move.

A 15-year-old high school sophomore from Westford, Nathan has earned international renown — and a nice chunk of money — by designing an artificial arm that can be moved around by signals from a person’s brain that are transmitted over a wireless Bluetooth device.

For now, the arm only waves from side to side, while its fingers flex in and out. Nathan cannot control it very precisely. But despite its limitations, Nathan’s mechanical arm is winning plenty of praise.

At last month’s Mobile World Congress in Barcelona, his arm won a $5,000 award for its innovative use of the Bluetooth radio technology found in most cellular phones. And last year, Nathan won $5,000 worth of electronics gear in a health care technology contest sponsored by the Army and Carnegie Mellon University.

Nathan is an avid technologist who writes iPhone apps and takes precollege classes at the Massachusetts Institute of Technology to improve his electrical engineering skills. But his interest in robotics was born in 2012, when he learned that one of his father’s relatives in India had lost both her forearms in an accident some years before.

“I decided to take matters into my own hands and design a prosthetic,” Nathan said.

Nathan’s father, Nanda, owner of Nova Write, a Hampstead, N.H., maker of industrial lasers, was happy to turn his son loose on the project.

“Early on I was thinking I could help him out,” he said, “but I soon realized I was getting in the way.”

Shiva Nathan spent months studying the literature on artificial limbs and learning how to build various components, such as fingers. Then he remembered a gift he had received from his uncle, a neuropediatrician: a Mindwave Mobile headset made by NeuroSky, of San Jose, Calif.

The headset, which can detect brain waves and transmit the signals to a computer or smartphone via Bluetooth, was designed to work with meditation software. By viewing his own brain waves on a personal computer display, a user can teach himself how to relax.

Nathan had lost interest in it for a while, but now he saw another use for it.

Nathan combined a mechanical hand and arm of his own design with a microcontroller and a Bluetooth radio receiver. He cannot move the hand and arm by thinking specific thoughts, such as “wave hello.” The headset detects only two mental states: attention and relaxation. When Nathan’s brain focuses on something specific, such as the number three, it transmits an attention signal, causing the hand’s fingers to flex.

When he clears his mind of specific thoughts, the elbow goes into action, waving the arm back and forth. Nathan is far from being able to pick up an egg or throw a punch just by thinking about it, but it is a crucial first step.

“This is leading-edge stuff,” said Errett Kroeter, director of global industry and brand marketing at Bluetooth Special Interest Group, the industry group that oversees Bluetooth technical standards. “If it were eventually turned into a commercial product, it would be of tremendous value.”

That is why Nathan’s brain-controlled arm beat out four other entrants in an innovation contest sponsored by the Bluetooth group.

Nathan’s idea has also impressed military experts on artificial limbs, such as John Fergason, lead prosthetist at the Brooke Army Medical Center in San Antonio. Fergason said Bluetooth is currently used to install new software in computerized artificial limbs, but that Nathan has gone much further in finding ways to control the limbs in real time.

“I think that’s a pretty doggone creative way to do it,” Fergason said.

Jay Schnitzer, director of biomedical science at Mitre Corp. in Bedford, a defense contractor, called Nathan’s achievement “pretty remarkable . . . it’s definitely going in the right direction, it’s addressing a real problem, and it’s a solution that’s really exciting.”

Schnitzer said the wireless control technology could prove equally useful for health care applications and as a way to control robots. “The two fields are joined at the hip, literally,” he said.

Nathan is now working on an upgraded arm with fingers that he will be able to control with a glance. Using Pupil, an eye-tracking technology developed at MIT, he hopes to figure out how to move individual fingers simply by looking at them.

Nathan hopes to someday work on robots at Google Inc. or iRobot Corp. in Bedford, or perhaps launch a prosthetics business. Until then, he plans to use the equipment he won in the Army contest to set up a science, engineering, and math education center in Westford.

As for the $5,000 cash prize, Nathan is going to give some of the money to charity. But because he is worried about his grades, most of the remaining money is going into a college fund “for those scholarships I don’t get.”