BEIJING – Open the app and tap a green button to “check in” once a day. Miss two consecutive check-ins and the app automatically sends an alert via e-mail to your designated emergency contact on the third day.

That is the concept of si le me – Mandarin for “ A re You Dead?” – a no-frills app that surged to the top of Apple’s App Store paid app ranking in China on Jan 10 and has since remained top of the chart, sparking widespread discussion on Chinese social media.