Dan Borislow, whose "MagicJack," peddled in television infomercials, helped pioneer free phone calls through the Internet, has died. He was 52.

Borislow died Monday of a heart attack after playing in a soccer game in West Palm Beach, Fla. His death was confirmed by Brad Shewmake, a spokesman for MagicJack Vocaltec Ltd., the maker of the device. Borislow was the founder and former chief executive of the company, based in Netanya, Israel, and West Palm Beach.

The company has sold more than 10 million MagicJack units, which connect to a computer's USB port or router to enable voice calls over the Internet. More than 25,000 retail stores sell the device.

Though calls are free, the product isn't: the latest version, the MagicJack Go, retails for $59.95, plus $35 for annual service after the first year, according to the company's website.

The device was promoted mostly in television infomercials. "Introducing MagicJack," said one, "the breakthrough device that makes your monthly phone bills disappear."

In a recent interview with Bloomberg News, Borislow said his invention was born from desperate times:

"I had a smartphone-like idea, in 2004," he said. "And I tried like hell. At the time, it was a Wi-Fi phone. We went to Taiwan to where the experts on Wi-Fi were at the time, and we tried — we must have had 30 prototypes of phones. I just couldn't make what would turn out like a smartphone.

"So I had $13 million invested of my own money, I had built up a hell of a telecom network while we were trying to make this Wi-Fi phone work — it was costing almost $1 million a month. So I had to come up with an idea, and fast, and really, out of desperation, I came up with the MagicJack."

An avid thoroughbred horse owner and racer, Borislow won $6.67 million in May by predicting the winners of six races at Gulfstream Park in Florida.

Borislow was born Sept. 21, 1961, in Philadelphia. His interest in innovation started when, at age 12, he acquired a fast lawn mower that enabled him to cut more grass at lower prices than his neighborhood competitors, according to a 2008 profile in the magazine of Widener University, his alma mater.

Before MagicJack, he was the founding chief executive of Tel-Save Holdings Inc., a long-distance telephone-service provider.

In 2011, Borislow bought the Washington Freedom, a team in the Women's Professional Soccer league. He renamed the team MagicJack and moved it to Boca Raton, Fla. Borislow feuded publicly and in court with the league, which folded in 2012.

Borislow had two children, Dan and Kylie, with his wife, Shelly.

Arnold and Coppola write for Bloomberg News.

news.obits@latimes.com