Just look at Zirtual[1] and Amicus[2][3].
[1] https://news.ycombinator.com/item?id=10036321
[2] http://www.newrepublic.com/article/119350/amicus-app-how-tec...
[3] https://news.ycombinator.com/item?id=8082785
Reply on news.ycombinator.com