SINGAPORE—Matt Walker, 34-year-old creator of the online authentication tool PassWindow, exhibits many of the familiar traits of the inventor: a restless desire to find a better way of doing things, the doggedness of the self-taught outsider—and a family tradition of innovation. In Mr. Walker's family, it was a grandfather who invented the Jarvis Walker fishing rod, a brand still beloved by many Australian fishermen. "He was the only cool thing in my extended family," the Brisbane native recalls. "I want to do this, because I think I can."

"This,"...