One time when I was day hiking Mount Washington, I took a wrong turn at the top and went down the wrong way. I raced down the mountain, but still had to navigate some rough terrain for a few hours in the dark. This was the late nineties.

When it comes to creating innovative apps to address municipal, environmental or social issues, the answer increasingly comes down to crowdsourcing . The public problem-solving site ChallengePost serves as a platform for innovative ideas from developers, working in areas as varied as the NYC subway system , the city's data feeds or the Surgeon General's Healthy Apps initiative. In a recent app challenge on the site, the US Department of Health and Human Services asked developers to address the issues of sexual assault and dating violence among college-age women.