BEIJING, Jan. 13 -- Tapping into a deep-seated fear among China's millions of solo dwellers - dying alone and unnoticed - a morbidly named new app called "Are You Dead?" has become a viral sensation, climbing to the top of the country's paid app charts.

The concept is simple: users must check in every two days by clicking a large button to confirm they are alive, BBC reported.

If they fail to do so, the app automatically notifies a pre-appointed emergency contact that they may be in trouble.

Launched with little fanfare last year, the app has recently exploded in popularity as it resonates with a growing demographic of young people who live alone, a group projected to reach 200 million by 2030.

"There is a fear that people living alon...