NEW YORK – It’s a maxim of technology: Invent the newest gadget and the porn industry will find a way to cash in.

So when Apple Inc. launched the iPhone 4 and its FaceTime videoconference feature, it didn’t take long for adult-entertainment companies to develop video-sex chat services and start hiring workers through Craigslist.

With more than 3 million of the phones already sold, the adult industry stands to make big money on this new way to reach out and touch someone – even if it puts Apple, which has always taken pains to keep its iPhone apps squeaky clean, in an awkward spot.

In at least five cities, Craigslist ads seek models specifically for video sex chat on FaceTime. FaceTime lets people call another iPhone 4 user and have live video conversations over a Wi-Fi connection using the front-facing camera on the new model. In one TV ad, a soldier uses it to get a look at his faraway wife’s ultrasound pictures.

The adult industry wants its customers to share moments of an entirely different kind with its stars. And while the technology may be new, the idea is not. Porn providers have always been early adopters.

In the 1970s, the demand for explicit videos at home helped VCRs become widespread, and the industry was the first to embrace DVDs. Internet porn peddlers were some of the first to make wide use of streaming video.

“The first time someone created a camera, there was someone who said, ‘Wouldn’t it be good for someone to take off their clothes in front of this camera?’ ” said Michael Gartenberg, vice president at Interpret LLC, a media research company.