Mobile health devices and software could change medicine profoundly, allowing people to continuously monitor vital signs and better track and modify behavior. That's important because chronic diseases like obesity and diabetes are on the rise. "We're seeing an infusion of mobile technologies into people's lives," says Susannah Fox, who studies technology and health care for the Pew Internet & American Life Project. "And we're seeing a very rainy forecast in terms of people's health."

In health care, however, good ideas often succumb to the realities of human nature. "Health isn't really top of mind for most of us," says Fox. Yet many health-related apps and devices essentially ask people to make health a priority. Pew's research has found that interest in health apps hasn't been increasing among users.

[Sonny] Vu's idea is to remove from the equation what he calls "intentionality"—the deliberate daily choice to use a health technology. Donning a pedometer or entering information into a calorie counter every day is asking too much of most people. "The best products are the ones that you really rely on but you don't have to remember to use," he says.

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