What does it mean that WeChat friends have set up health guards?

Help users protect their health. Health Guarding is a function set by WeChat friends, which helps users to protect their health by intelligently detecting the content of users' circle of friends, reminds users to control their sleep time, and enables users to develop healthy living habits. Wechat is a free application launched by Tencent on 2011121,which provides instant messaging service for intelligent terminals.