SAN FRANCISCO, United States — Twitter Inc. Chief Executive Officer Dick Costolo said the online service for 140-character messages is increasingly being used to track personal health with wearable computing gadgets such as Nike Inc.'s fitness devices.

“People are readily tweeting things out from wearable devices” Costolo said today at the National Venture Capital Association’s annual conference in San Francisco. “There’s a huge opportunity in the health-care space.”

Twitter is expanding into smartphones and other wireless products, seeking to boost the number of users and advertisers. In addition to transmitting exercise data via Twitter posts, Costolo sees other applications in health care, such as scales that can automatically post a user’s weight to a website.

Engineers at the social website are also looking at ways to adapt the service for use with Google Inc.’s Glass, the wearable mobile-computing device resembling spectacles, John Doerr, general partner at Kleiner Perkins Caufield & Byers, a Twitter investor, said last month.

San Francisco-based Twitter, founded in 2006, has nearly 2,000 employees, Costolo said.

By: Douglas MacMillan; Editors: Reed Stevenson, Ben Livesey